Plant Species Over-Occupancy Indicates River Valleys Are Natural Corridors for Migration

River valleys are considered natural corridors for migration of plant species, however, there is a lack of studies confirming higher colonisation rates of plant species in these areas. We compare plant species-richness between ancient and recent forests, and those located in a river valley with those located in the surrounding landscape. We hypothesise that, close to a river, higher plant species-richness will be associated with recent forests thus indicating a higher colonisation rate. The study area includes part of the Elbe River Valley and its surrounding landscape in the Czech Republic. We sampled an equal number of recent and ancient forests but lying at different distances from the river. We used generalised linear models to test the effect of distance from the river in dependence upon forest continuity (recent/ancient forest) on two plant species-richness categories, i.e. richness of forest species and overall species richness. In the surrounding landscape, higher richness of forest species was associated with ancient forests, whereas overall species richness was comparable. In the river valley, richness of forest species as well as overall species richness was higher in the recent forests. Recent forests in the river valley were more saturated by plant species than those in the surrounding landscape, indicating that in the river valley the colonisation rate of plant species is higher. These results confirm the importance of river valleys as natural corridors for migration of plant species.

Tree Rings Reveal How Ancient Forests Were Managed

By analyzing thousands of oak timbers dating from the 4th to 21st centuries, scientists have pinpointed the advent of a forest management practice.

Fire-scarred fossil tree from the Late Triassic shows a pre-fire drought signal

Exploring features of wood anatomy associated with fire scars found on fossil tree trunks is likely to increase our knowledge of the environmental and ecological processes that occurred in ancient forests and of the role of fire as an evolutionary force. In Petrified Forest National Park, Arizona, where Late Triassic fossil trees are exposed, we found 13 examples of fossil logs with external features resembling modern fire scars. One specimen with the unambiguous external features of a fire scar was collected for analysis of its fossilized wood. A light-colored band composed of compressed and distorted tracheids was associated with the scarring event. Cell lumen diameter and cell wall thickness in the pre-scarring fossilized wood show a response similar to that described in modern trees experiencing drought conditions. Tracheids in the post-scarring wood are initially smaller, and then become larger than average following a recovery period, as is often observed in modern conifers following fire. The responses in external morphology and wood anatomy to drought and fire were similar to those of some modern trees and support the view that some forests may have experienced conditions favoring the evolution of fire-adapted traits for more than 200 million years.

From taxonomic to functional dark diversity: exploring the causes of potential biodiversity and its implications for conservation

Aims and context: Dark diversity is an emerging and promising concept proposed to estimate the recruitment potential of natural communities and guide conservation and restoration policies. It represents all the species that could be present in a community due to favourable environmental conditions, but are currently lacking. To date, experimental approaches only measured taxonomic dark diversity, mainly based on species coexistence, which relies partly on neutral processes. Thus, these approaches may fail to identify the biodiversity which is lacking for deterministic reasons, and can hence hardly bring out suitable restoration methods. Methods: Here, we propose a novel method to estimate dark diversity, which is based on more deterministic coexistence: the coexistence of functional features. We adapted the Beals co-occurrence index using functional groups, and we estimated functional dark diversity based on coexistence of functional groups. We then made use of functional dark diversity to address a persistent issue of restoration ecology: how does passive rewilding impact the ecological integrity of recovered communities? We compared spontaneous, secondary woodlands with ancient forests, in terms of taxonomic and functional dark diversity of vascular plants and spiders. Results: Our results indicated that functional dark diversity does not equate to taxonomic dark diversity. Considering plants, recent woodlands surprisingly harboured less functional dark diversity than ancient forests, while they had a very similar amount of taxonomic dark diversity. Concerning spiders, recent woodlands harboured a similar amount of functional dark diversity as ancient forests, but more taxonomic dark diversity. Also, the composition of functional dark diversity differed between forest types, shedding light on their past assembly processes and unveiling their potential for conservation and effective restoration. Synthesis: Functional dark diversity brings novel perspectives for ecological diagnostic and restoration. Combined to taxonomic dark diversity, it enables to identify easily the deterministic constrains which limit the re-assembly of ecological communities after land-use changes and to predict the realistic, possible establishments of functional features. Here, we showed that spontaneous woodlands can have very similar, sometimes even higher, ecological integrity than that of ancient forests, and hence may be valuable habitats to be conserved from an ecological perspective.