RecruitNet: A global database of plant recruitment networks.

Plant recruitment interactions (i.e., what recruits under what) shape the composition, diversity, and structure of plant communities. Despite the huge body of knowledge on the mechanisms underlying recruitment interactions among species, we still know little about the structure of the recruitment networks emerging in ecological communities. Modeling and analyzing the community-level structure of plant recruitment interactions as a complex network can provide relevant information on ecological and evolutionary processes acting both at the species and ecosystem levels. We report a data set containing 143 plant recruitment networks in 23 countries across five continents, including temperate and tropical ecosystems. Each network identifies the species under which another species recruits. All networks report the number of recruits (i.e., individuals) per species. The data set includes >850,000 recruiting individuals involved in 118,411 paired interactions among 3318 vascular plant species across the globe. The cover of canopy species and open ground is also provided. Three sampling protocols were used: (1) The Recruitment Network (RN) protocol (106 networks) focuses on interactions among established plants ("canopy species") and plants in their early stages of recruitment ("recruit species"). A series of plots was delimited within a locality, and all the individuals recruiting and their canopy species were identified; (2) The paired Canopy-Open (pCO) protocol (26 networks) consists in locating a potential canopy plant and identifying recruiting individuals under the canopy and in a nearby open space of the same area; (3) The Georeferenced plot (GP) protocol (11 networks) consists in using information from georeferenced individual plants in large plots to infer canopy-recruit interactions. Some networks incorporate data for both herbs and woody species, whereas others focus exclusively on woody species. The location of each study site, geographical coordinates, country, locality, responsible author, sampling dates, sampling method, and life habits of both canopy and recruit species are provided. This database will allow researchers to test ecological, biogeographical, and evolutionary hypotheses related to plant recruitment interactions. There are no copyright restrictions on the data set; please cite this data paper when using these data in publications.

Quantifying the effects of Robinia pseudoacacia afforestation on plant community structure from a functional perspective: New prospects for management practices on the hilly and gullied Loess Plateau, China.

Robinia pseudoacacia is regarded as a valuable but problematic plant due to its positive and negative environmental effects. A comprehensive and mechanistic understanding of the effects of R. pseudoacacia afforestation on ecosystems and striking a balance between ecosystem safety and functioning and R. pseudoacacia naturalization are crucially important. To achieve these goals, studying the community functional structure of R. pseudoacacia plantations is an essential prerequisite that remains understudied. Through quantifying and comparing the functional structure of R. pseudoacacia plantations and naturally restored communities relating to soil erosion control and plant ecology strategies along a 10-40-year chronosequence on the hilly and gullied Loess Plateau, China, we assessed the effects of R. pseudoacacia afforestation on plant community structure from a functional perspective. We found significant differences among restoration strategies in all the functional composition indices but only functional divergence (FDiv) indices, suggesting that the afforestation practice had a great impact on functional composition but not on functional diversity. Specifically, the plantations had relatively high community-weighted means (CWMs) of specific leaf area (SLA), plant height (PH), seed production, seed mass, root mean diameter, clonality and resprouting capacity and high FDivs of the leaf-height-seed scheme and persistence traits, partially suggesting that the exotic tree could naturalize and coexist with native plants in the study area. Moreover, the relatively high CWMs of woodiness, PH and SLA and high FDiv of erosion-control-related traits found in the plantations indicate that the plantations might have superiority in soil erosion control. R. pseudoacacia also had a homogenization effect on understory functional composition and divergence. Furthermore, we proposed a trait-based effect-and-response framework to find the balance, thus achieving sustainable coexistence of the exotic species with ecosystems. This study may provide new prospects for management practices of R. pseudoacacia plantations and a robust scaffold to maintain safe, resilient and functioning ecosystems.

Increasing aridity threatens the sexual regeneration of Quercus ilex(holm oak) in Mediterranean ecosystems.

Knowledge of the recruitment of dominant forest species is a key aspect for forest conservation and the ecosystem services they provide. In this paper, we address how the simultaneous action of climate change and the intensity of land use in the past influence the recruitment of a forest species that depends on the provision of nurse plants to recruit. We compared the number of saplings (up to 15 years old) and juveniles (16 to 50 years old) of Quercus ilex in 17, 5.3 ha plots in the Iberian System (eastern Spain). We used a gradient of past deforestation intensity crossed with two levels of average annual precipitation, one of them at the lower limit of the species' precipitation niche (semi-arid) and the other at the optimum (sub-humid). We also examined the association between recruits and nurse plants and the effect on this association of plot-scale factors, such as seed abundance (reproductive Q. ilex), microsites (nurse species and soil availability), and large herbivores. The increase in aridity in the last decades has drastically reduced the recruitment of new individuals in the forests of Q. ilex located in the lower limit of their precipitation niche, regardless of the intensity of past deforestation that they suffered. Recruitment in these climatic conditions depends almost exclusively on large trees and shrubs whose abundance may also be limited by aridity. The lack of regeneration questions the future of these populations, as the number of individuals will decrease over time despite the strong resistance of adult trees to disturbance and drought.

Functional and evolutionary correlations of steep leaf angles in the mexical shrubland.

In the evergreen shrubland vegetation of Mexico (mexical), most of the species are sclerophyllous woody plants with steep leaf angles. This architectural pattern has been interpreted as a strategy to cope with water shortages and high radiation. However, the current association between evergreenness and steep leaf angles across mexical plant species could be the result of an adaptive association achieved through correlated evolutionary change between both traits or, alternatively, may be the result of common evolutionary ancestry. In this study, we quantified leaf angle in 28 dominant species under a phylogenetic framework and evaluated the functional implications of the observed range of leaf angles in terms of leaf temperature, water potentials and transpiration by combining manipulative experiments restraining leaves horizontally with microclimatic and stomatal conductance measurements in selected species and energy balance calculations. Horizontally restrained leaves exhibited reduced water potentials and stomatal conductances, and significantly increased temperatures and transpiration rates. Steeply inclined leaves operated near air temperatures and could sustain relatively high stomatal conductances during the dry season since they were associated with low transpiration rates. Phylogenetic analyses showed that steep leaf angles evolved in a correlated fashion in evergreen species. The functional consequences of leaf angle together with the phylogenetic analysis indicate the adaptive nature of this trait which allows the evergreen species to cope with arid conditions and therefore to persist within the mexical community.