Practice Must Be Backed up by Theory! A Special Issue on Plant Community Ecology

Plant communities form the structural and functional basis for nearly all terrestrial ecosystems [...]

Patterns of Co-occurrence of Rare and Threatened Species in Winter Arable Plant Communities of Italy

Detecting patterns of species co-occurrence is among the main tasks of plant community ecology. Arable plant communities are important elements of agroecosystems, because they support plant and animal biodiversity and provide ecosystem services. These plant communities are shaped by both agricultural and environmental drivers. The pressure of intensive agriculture worldwide has caused the decline of many characteristic arable species and communities. Italy is the European country where arable plant biodiversity is the best preserved. In this study, we assessed the patterns of co-occurrence of rare and threatened arable plants in 106 plots of winter arable vegetation located from Piedmont to Calabria, in the mainland part of the country. For this purpose, we based our investigation on the analysis of a recently acquired dataset and on the European list of rare and threatened arable plants. We highlight how different species of conservation interest tend to occur in the same community. On the other hand, generalist and more competitive taxa show similar patterns of co-occurrence. We suggest that single species of conservation value could be suitable indicators of a well-preserved community. On the other hand, to be effective, conservation strategies should target the whole community, rather than single species.

The ecology of plants: from seed to seed

This chapter deals with the ecology of Tropical East Asia from a plant perspective. The life cycle of forest trees is covered in detail, including their vegetative and reproductive phenology, pollination, seed dispersal, seed predation, and the seedling, sapling, and adult stages. Other life forms, including lianas, ground herbs, epiphytes, hemi-epiphytes, and parasites are considered in less detail. Recent advances in plant community ecology are discussed, including the mechanisms responsible for the maintenance of species diversity in tropical forests (niche differentiation, growth–survival trade-offs, conspecific negative density-dependent mortality, neutral theory), and the influence of functional traits and phylogeny on community assembly. Forest succession is discussed in a regional context.

Deep learning for weed identification based on seed images

Reliable plant species identification from seeds is intrinsically difficult due to the scarcity of features and because it requires specialized expertise that is becoming increasingly rarer, as the number of field plant taxonomists is diminishing (Bacher 2012, Haas and Häuser 2005). On the other hand, seed identification is relevant in some science domains such as plant community ecology, archaeology, paleoclimatology. Besides, economic activities such as agriculture, require seed identification to assess weed species contained in the "soil seed banks" (Colbach 2014) to enable targeted treatments before they become a problem. In this work, we explore and evaluate several approaches by using different training image sets with various requisites and assessing their performance with test datasets of different sources. The core training dataset is provided by the Anthos project (Castroviejo et al. 2017) as a subset of its image collection. It consists of nearly a 1000 images of seeds identified by experts. As identification algorithm, we will use state-of-the-art convolutional neural networks for image classification (He et al. 2016). The framework is fully written in Python using the TensorFlow (Abadi et al. 2016) module for deep learning.

Applying the centrifugal organizational model for pastoralists and other competing communities on the Ethiopian landscape and the shift to agriculture after 1975

For the past four decades pastoralist activities have been pushed to marginal areas in several regions of Ethiopia. This change was initiated by The Agrarian Land Reform Proclamation of 1974. Pastoralist activities prior to the agrarian reforms was strongly connected to the Earth and developed symbiotically. A connection to the Earth through symbiotic relationships has been shown to foster sustainability. There are a few goals of this paper: 1. to apply the centrifugal organizational model, originally synthesized in the field of plant community ecology, to the changing environment and pastoralism in Ethiopia, 2. to demonstrate a shift from periphery habitat to the core habitat with respect to land use since the agrarian reform in 1974, 3. to demonstrate a loss of connectedness with the Earth in regions of Ethiopia.

Differences in topographic and soil habitat specialization between trees and two understorey plant groups in a Costa Rican lowland rain forest

Two core questions in plant community ecology are to what extent the distributions of species are structured by local environmental conditions, and whether taxa differ in this regard. We compared the distributions of trees, Melastomataceae and ferns on soil and topographic gradients in a Costa Rican lowland rain forest (trees and ferns 983 plots, Melastomataceae 277 plots). To test whether these plant groups differed in the prevalence or type of habitat specialization, we calculated species’ environmental optima and tolerances on each gradient. Habitat specialization was defined as a significantly biased optimum, or a narrow tolerance, relative to values obtained under spatially restricted randomizations of species occurrences. Within plant groups, we also asked whether the dispersion of species optima differed from random expectation on each gradient. Fern optima were over-dispersed on multiple gradients, implying considerable interspecific habitat partitioning, and tree optima were over-dispersed in relation to topographic position. Habitat specialization was more prevalent in the two predominantly understorey groups than in trees (75% of Melastomataceae species, 81–87% of ferns, 57–58% of trees). Species optima of Melastomataceae and ferns also tended towards lower landscape positions than did those of trees, perhaps reflecting a higher proportion of drought-sensitive species in these two groups.