Structure Of Plant Assemblages Research Articles

Forest encroachment into a Californian grassland: examining the simultaneous effects of facilitation and competition on tree seedling recruitment

Competition and facilitation are both considered major factors affecting the structure of plant assemblages, yet few studies have quantified positive, negative, and net effects simultaneously. In this study, we investigated the positive, negative, and net effects of tree saplings on the encroachment of two tree species, Douglas fir (Pseudotsuga menziesii) and tanoak (Lithocarpus densiflora), into a coastal California grassland. The study involved three components: sampling the spatial distributions of P. menziesii and L. densiflora in the grasslands, a field experiment examining seedling survival in different grassland environments, and a greenhouse experiment examining the effects of soil moisture on early seedling performance. The field experiment was conducted over a 2-year period, using Pseudotsuga in 2002 and both species in 2003. Seedlings were separated into four treatment groups: those planted in open grassland, in shaded grassland, under artificial (plastic) conifer saplings, and under natural Pseudotsuga saplings. Air temperature, relative humidity, soil moisture, incident radiation levels and fog water inputs were measured for each treatment group in 2003. In the greenhouse experiment, Pseudotsuga and Lithocarpus seedlings were grown for 13 weeks in watering treatments simulating the summer soil moisture conditions of the open grasslands and under Pseudotsuga saplings. Surveys of naturally established seedlings found that Lithocarpus occurred only under Pseudotsuga saplings, while most Pseudotsuga seedlings were located near but not directly under conspecific saplings. In the field experiment, positive effects of tree saplings were much larger than negative effects, resulting in strong net facilitation of seedling establishment. Survival for both species was always higher under the plastic and live trees than in the open or shade plots. The primary mechanism facilitating seedling survival appeared to be increased soil moisture caused by input of fog precipitation coupled with reduced microsite evaporation. The greenhouse experiment further showed that soil moisture strongly affected seedling performance, with both species having much higher photosynthetic rates in the higher moisture treatment. In the lower moisture treatment, Pseudotsuga seedlings had higher photosynthetic rates and stomatal conductance than Lithocarpus, suggesting they may be able to better tolerate the environmental conditions found in the open grasslands. Our combined results suggest that rate and patterning of woody plant encroachment can be strongly influenced by facilitation and that fog precipitation may play a key role in plant interactions.

Relation of Soil and Vegetation on Sandy Sea Shores

Next article FreeRelation of Soil and Vegetation on Sandy Sea ShoresPehr Olsson-SefferPehr Olsson-Seffer Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by Volume 47, Number 2Feb., 1909 Article DOIhttps://doi.org/10.1086/329816 Views: 66 Citations: 6Citations are reported from Crossref Journal History This article was published in the Botanical Gazette (1876-1991), which is continued by International Journal of Plant Sciences (1992-present). PDF download Crossref reports the following articles citing this article:Marius-Nicusor Grigore Definition and Classification of Halophytes as an Ecological Group of Plants, (May 2021): 3–50.https://doi.org/10.1007/978-3-030-57635-6_1Marius-Nicușor Grigore Definition and Classification of Halophytes as an Ecological Group of Plants, (Aug 2020): 1–48.https://doi.org/10.1007/978-3-030-17854-3_1-1Marinka E. B. Puijenbroek, Corry Teichmann, Noortje Meijdam, Imma Oliveras, Frank Berendse, Juul Limpens Does salt stress constrain spatial distribution of dune building grasses Ammophila arenaria and Elytrichia juncea on the beach?, Ecology and Evolution 7, no.1818 (Aug 2017): 7290–7303.https://doi.org/10.1002/ece3.3244Brett A. McMillan, Frank P. Day Micro-Environment and Plant Assemblage Structure on Virginia's Barrier Island “Pimple” Dunes, Northeastern Naturalist 17, no.33 (Sep 2010): 473–492.https://doi.org/10.1656/045.017.0308T. R. Dudley, G. E. Crow A Contribution to the Flora and Vegetation of Isla de los Estados (Staten Island), Tierra del Fuego, Argentina, 37 (Jan 1983).https://doi.org/10.1029/AR037Mark A. Benedict , history of, (Jul 2014): 301–310.https://doi.org/10.1007/0-387-30843-1_123