No abstract

Soil organisms provide crucial ecosystem services that support human life. However, little is known about their diversity, distribution, and the threats affecting them. Here, we compiled a global dataset of 60 sampled earthworm communities from over 7000 sites in 56 countries to predict patterns in earthworm diversity, abundance, and biomass. We identify the environmental drivers shaping these patterns. Local species richness and abundance typically peaked at higher latitudes, while biomass peaked in the tropics, patterns opposite to those observed in aboveground organisms. Similar to many aboveground taxa, climate variables were more important in shaping earthworm communities than soil properties or habitat 65 cover. These findings highlight that, while the environmental drivers are similar, conservation strategies to conserve aboveground biodiversity might not be appropriate for earthworm diversity, especially in a changing climate.

This study evaluates the hypothesis that biological grazing refuges have an important role in plant‐grazer interactions of grasslands with a long history of grazing. We assessed the hypothesis that clumps of the spiny cactus Opuntia polyacantha provide biological refuges from cattle grazing, affecting cover and seedhead production of associated vascular plants in the shortgrass steppe of the North America. The study was based on sampling inside and outside Opuntia clumps in eight long‐term moderately grazed pastures established 60 yr ago and their respective ungrazed controls. Opuntia clumps provided a refuge for seedhead production of the dominant grass (Bouteloua gracilis) and for cover and seedhead production of many plant groups. Clumps were also a refuge for species sensitive to grazing (species that decrease with grazing) and barrel‐cacti, but not for species preferred by cattle (species with greater proportion in the diet than in the field), exotics or weeds. Our results suggest that these effects were mainly through changes in the microenvironmental conditions resulting from protection effects, even though all potential microenvironmental effects could not be measured. Cacti promoted some negative effects on other plant groups, probably due to the space occupied by cladodes inside cactus clumps. The refuge effects observed at the group level did not translate into strong community level effects. Species diversity (H′) was greater in cactus clumps due to lower dominance rather than greater richness. The presence of Opuntia clumps increased landscape‐scale diversity. This ecological role of Opuntia clumps as refuge from cattle grazing should be taken into consideration in management practices aimed at cactus eradication in order to increase forage availability for livestock. We discuss the potential role of plant community productivity and grazing history with regard to the importance of natural refuges in structuring grassland communities.

A. 2001. Recruitment in a Mediterranean annual plant community: seed bank, emergence, litter, and intra-and inter-specific interactions. -Oikos 95: 485-495.Recruitment of reproductive individuals in plant communities is influenced by multiple interacting factors which can be arranged in a number of sequential and distinct stages. Numerous studies have addressed the issue of recruitment in relatively simple conditions under experimental constraints (see Harper 1977, Fenner and Kitajima 1999, Fenner 2000 for extensive reviews). However, it is necessary to approach the subject by testing multiple causal factors within a community context under field conditions. Recruitment of reproductive individuals of annual plants depends chiefly on the abundance of germinable seeds, and emergence and survival of seedlings. Abundance of germinable seeds has been found to be a key factor, particularly in early successional phases (Moore 1980). Under such dynamical conditions, species com-

Summary1. Some plant functional traits evolved with high temporal resource variability and disturbance in ecosystems where these factors are prevalent. Persistence of characteristics of these functional traits in ecosystems may depend on continued resource variability and disturbance, which in turn may promote functional diversity. In Mediterranean ecosystems, experiments that eliminate temporal resource variability and disturbance are needed to detect functional trait dependence on these factors. 2. The purpose of this study was to experimentally assess how interannual rainfall variability, summer drought and seasonal grazing modify the characteristics of functional traits (life span, flowering time, seed size and plant size) in old-field (6-15 years) Mediterranean herbaceous communities. 3. We designed a 9-year factorial field experiment that manipulated Mediterranean rainfall variability in three ways: (i) constant water availability with no summer drought; (ii) autumn and spring water availability but with summer drought; and (iii) no water supplied to rainfall; and grazing regimes: (i) autumn grazing; (ii) spring grazing; and (iii) non-grazing, in each of the three scenarios of water availability. At a community scale, we measured abundance of different categories within four plant functional traits: plant life span (annual and perennial), flowering time of annuals (spring and summer) and seed and plant sizes of spring annuals (small and large). 4. Interannual rainfall variability in autumn and spring (IRVAS), summer drought and grazing reduced perennial cover. IRVAS was necessary for the persistence of small-seeded and small-size spring annuals. IRVAS and summer drought increased spring annuals in grazed treatments. 5. Results suggest that IRVAS, summer drought and grazing favour the coexistence of species, through improved functional diversity in seed and plant sizes and increased abundance of spring annuals, the most species-rich functional group. Both effects may be the reason for the high species richness in grazed Mediterranean herbaceous communities.

Diet studies present numerous methodological challenges. We evaluated the usefulness of commercially available trail-cameras for analyzing the diet of Northern Goshawks (Accipiter gentilis) as a model for nesting raptors during the period 2007–2011. We compared diet estimates obtained by direct camera monitoring of 80 nests with four indirect analyses of prey remains collected from the nests and surroundings (pellets, bones, feather-and-hair remains, and feather-hair-and-bone remains combined). In addition, we evaluated the performance of the trail-cameras and whether camera monitoring affected Goshawk behavior. The sensitivity of each diet-analysis method depended on prey size and taxonomic group, with no method providing unbiased estimates for all prey sizes and types. The cameras registered the greatest number of prey items and were probably the least biased method for estimating diet composition. Nevertheless this direct method yielded the largest proportion of prey unidentified to species level, and it underestimated small prey. Our trail-camera system was able to operate without maintenance for longer periods than what has been reported in previous studies with other types of cameras. Initially Goshawks showed distrust toward the cameras but they usually became habituated to its presence within 1–2 days. The habituation period was shorter for breeding pairs that had previous experience with cameras. Using trail-cameras to monitor prey provisioning to nests is an effective tool for studying the diet of nesting raptors. However, the technique is limited by technical failures and difficulties in identifying certain prey types. Our study also shows that cameras can alter adult Goshawk behavior, an aspect that must be controlled to minimize potential negative impacts.

Scatter-hoarding animals such as corvids play a crucial role in the dispersal of nut-producing tree species. This interaction is well known for some corvids, but remains elusive for other species such as the magpie (Pica pica), an abundant corvid in agroecosystems and open landscapes of the Palearctic region. In addition, the establishment of the individual dispersed seeds-a prerequisite for determining seed-dispersal effectiveness-has never before been documented for the interaction between corvids and nut-producing trees. We analyzed walnut dispersal by magpies in an agroecosystem in southern Spain. We used several complementary approaches, including video recording nut removal from feeders, measuring dispersal distance using radio tracking (with radio transmitters placed inside nuts), and monitoring the fate of dispersed nuts to the time of seedling emergence. Magpies were shown to be highly active nut dispersers. The dispersal distance averaged 39.6 ± 4.5 m and ranged from 4.1 to 158.5 m. Some 90% of the removed walnuts were cached later, and most of these (98%) were buried in the soil or hidden under plant material. By the time of seedling emergence, ca. 33% of nuts remained at the caching location. Finally, 12% of the cached nuts germinated and 4% yielded an emerged seedling, facilitating the transition to the next regeneration stage. The results demonstrate for the first time that magpies can be an effective scatter-hoarding disperser of a nut-producing tree species, suggesting that this bird species may play a key role in the regeneration and expansion of broadleaf forests in Eurasia.

Prey preferences and recent changes in diet of a breeding population of the Northern Goshawk Accipiter gentilis in Southwestern Europe. Bird Study, 64(4), pp. 464-475.