Comment on "The global tree restoration potential".

Bastin 's estimate (Reports, 5 July 2019, p. 76) that tree planting for climate change mitigation could sequester 205 gigatonnes of carbon is approximately five times too large. Their analysis inflated soil organic carbon gains, failed to safeguard against warming from trees at high latitudes and elevations, and considered afforestation of savannas, grasslands, and shrublands to be restoration.

Author Correction: Diversity-dependent temporal divergence of ecosystem functioning in experimental ecosystems.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Resources for Crop Production: Accessing the Unavailable.

An acute imbalance between human population and food production is projected, partially due to increasing resource scarcity; dietary shifts and the current course of technology alone will not soon solve the problem. Natural ecosystems, typically characterized by high species richness and perennial growth habit, have solved many of the resource-acquisition problems faced by crops, making nature a likely source of insights for potential application in commercial agriculture. Further research on undomesticated plants and natural ecosystems, and the adaptations that enable them to meet their needs for N, P, and water, could change the face of commercial food production, including on marginal lands.

Diversity-dependent temporal divergence of ecosystem functioning in experimental ecosystems.

The effects of biodiversity on ecosystem functioning generally increase over time, but the underlying processes remain unclear. Using 26 long-term grassland and forest experimental ecosystems, we demonstrate that biodiversity-ecosystem functioning relationships strengthen mainly by greater increases in functioning in high-diversity communities in grasslands and forests. In grasslands, biodiversity effects also strengthen due to decreases in functioning in low-diversity communities.

Tree species identity and interactions with neighbors determine nutrient leaching in model tropical forests.

An ecosystem containing a mixture of species that differ in phenology, morphology, and physiology might be expected to resist leaching of soil nutrients to a greater extent than one composed of a single species. We tested the effects of species identity and plant-life-form richness on nutrient leaching at a lowland tropical site where deep infiltration averages >2 m year(-1). Three indigenous tree species with contrasting leafing phenologies (evergreen, dry-season deciduous, and wet-season deciduous) were grown in monoculture and together with two other life-forms with which they commonly occur in tropical forests: a palm and a giant, perennial herb.

Water use in four model tropical plant associations established in the lowlands of Costa Rica.

We examined soil water use patterns of four model plant associations established in the North Caribbean lowlands of Costa Rica by comparing the stable hydrogen isotope composition, deltaD, in xylem sap and in soil water at different depths, under rainy and dry conditions. Four 5-year-old model plant associations composed of 2 tree species (Hyeronima alchorneoides and Cedrela odorata) having different architecture and phenology were studied. Average tree height was 8.

Competition from below for light and nutrients shifts productivity among tropical species.

Chance events such as seed dispersal determine the potential composition of plant communities, but the eventual assemblage is determined in large part by subsequent interactions among species. Postcolonization sorting also affects the ultimate composition of communities assembled by people for restoration, horticulture, or conservation. Thus, knowledge of the mechanisms controlling interspecific interactions in plant communities is important for explaining patterns observed in nature and predicting success or failure of utilitarian combinations.

Species and rotation frequency influence soil nitrogen in simplified tropical plant communities.

Among the many factors that potentially influence the rate at which nitrogen (N) becomes available to plants in terrestrial ecosystems are the identity and diversity of species composition, frequency of disturbance or stand turnover, and time. Replicated suites of investigator-designed communities afforded an opportunity to examine the effects of those factors on net N mineralization over a 12-year period. The communities consisted of large-stature perennial plants, comprising three tree species (Hyeronima alchorneoides, Cedrela odorata, and Cordia alliodora), a palm (Euterpe oleracea), and a large, perennial herb (Heliconia imbricata).

Links between tree species, symbiotic fungal diversity and ecosystem functioning in simplified tropical ecosystems.

We studied the relationships among plant and arbuscular mycorrhizal (AM) fungal diversity, and their effects on ecosystem function, in a series of replicate tropical forestry plots in the La Selva Biological Station, Costa Rica. Forestry plots were 12 yr old and were either monocultures of three tree species, or polycultures of the tree species with two additional understory species. Relationships among the AM fungal spore community, host species, plant community diversity and ecosystem phosphorus-use efficiency (PUE) and net primary productivity (NPP) were assessed.

Developmental and physiological correlates of leaf size in Hyeronima alchorneoides (Euphorbiaceae).

The tropical emergent tree Hyeronima alchorneoides has large decreases in leaf size with tree age: 1200 cm(2) at 1 yr, 900 cm(2) at 3 yr, 200 cm(2) at 11 yr, and 80 cm(2) in old (>30 yr) individuals. We tracked leaf growth and physiological attributes on trees of three different ages (1, 3, and 11 yr) to determine the developmental basis and functional consequences of this variation. Leaves on young trees grew faster and sustained maximum rates of leaf expansion longer than leaves on older trees.

Nitrogen isotope ratios shift with plant size in tropical bromeliads.

We describe an ontogenetic shift in nitrogen (N) isotopic values in two rosette-forming epiphytic bromeliads. Leaf tissue N isotope values of small individuals of two bromeliad species (mean -6.2 per thousand ) differed from those of large individuals within each species (mean -0.

Tropical Soil Fertility Changes Under Monocultures and Successional Communities of Different Structure.

For 5 yr we monitored the fertility of a volcanic-ash derived Inceptisol at a site in the humid tropics of Costa Rica. After forest felling and burning, we established four treatments in a randomized block design with six blocks: a sequence of monocultures (two crops of maize [Zea mays] followed by cassava [Manihot esculenta], then the tree species Cordia alliodora), successional vegetation, a mimic of successional vegetation that was physiognomically similar to the model but shared no species with it, and a species-enriched version of successional vegetation. In addition, one plot was maintained free of vegetation.