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Photos & text

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Photos & texts by Sabina Burrascano is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 2.5 Italy License.
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The massive take over of flowers

A paper that absolutely deserves your time, even if you are not a specialist in the field (also because it is free for anyone online), is the one by Frank Berendse and Marten Scheffer (Ecology letters 12: 865-872).

I report here some of their observations and conclusions.

Charles darwin, the author of the On the origin of species, great contributor to the explanation of biological diversification on Earth, was puzzled by an abominable mistery: the angiosperm radiation in the Cretaceous period.

Angiosperms (or flowering plants) were 5-20% of the vascular plant species about 105 millions of years ago (Ma), when gimnosperms dominated the landscape and ferns where much more abundant. Nevertheless, they reached 80-100% about 65 Ma.

In this period flowering plants became more abundant and more diverse at a very impressive rate.

Before this radiation early angiosperms were limited to disturbed sites, while tall conifer forests with a dense fern understory were   definitely dominant.

At some time during the Cretaceous flowering plants entered the fern dominated understory and later angiosperms trees started to play an prominent role. This explains why the decline of ferns was more marked, while gimnosperms’ decline occured later and more slowly.

Several explanations have been proposed for this rapid and massive process, on the linked paper you can read a synthesis of several hypothesis and their limits. On the other hand, the authors relate the great take over of flowering plants to their differences in ecological requirements and litter quality. In fact the authors propose that the massive scale of shift in Earth vegetation composition may be explained as a result of a positive feedback between angiosperms and their environment.

Flowering plants have higher growth rates and need higher nutrient levels than the gimnosperms; at the same time they promote soil nutrient levels by producing litter that is more readily decomposed. In contrast gimnosperms do relatively well under low nutrient conditions and mantain low nutrient levels in the soil due to the nature of their litter.

In fact, gimnosperms generally have longer leaf life span , higher lignin concentration and low nutrients (N and P) concentrations. Their strategy aims at increasing the carbon assimilation per unit of adsorbed nutrient and reduce nutrient losses. Angiosperms require and create a higher soil nutrient levels.

Once flowering plants are present in sufficient densities they enhance soil fertility through litter implying a positive feedback that might produce a runaway process once angiosperms have reached a certain critical abundance.

Evidence for this hypothesis comes from recent vegetation shifts monitored by long-term field observations: the change from ericaceous dwarf shrubs (with leaf traits similar to gimnosperms) dominated communities (heathlands) to monospecific stands of perennial grasses (Molinia caerulea) in Western Europe; and the expansion of dwarf shrubs and graminoid in bog ecosystemsoriginally dominated by conifer trees.

Molinia caerulea dominated landscape in WalesConifer trees in a bog, Vermont - U.S.A.

In both cases an increase in nutrient supply (due to the abandonment by farmers in heathlands and by N-pollution in bogs) led to a rapid increase of flowering plants to the detriment of conifers and species with gimnosperms-like strategies.

I think that the integration of data coming from fossils and recent vegetation shifts and, above all, an ecological perspective make this hypothesis likely and definitely fascinating.

Convallaria majalis day by day

Convallaria majalis

Convallaria majalisConvallaria majalisConvallaria majalis

Bug in LEDA traitbase

Using LEDA database on plants functional traits I found out a bug with regards to clonal growth traits.

I wrote to the authors and they blocked this trait for the moment.

However if after reading my post you downloaded information on clonal growth from LEDA double-check it and wait for the bug to be fixed!

Why are tropical rainforests so diverse?

Alas Purwo National Park, Timur Java, IndonesiaThis title is shared with one paragraph of one of my favourite readings, perfect for friday late afternoon: The Encyclopedia of Biodiversity. I report here some of the concepts recalled in that paragraph by I.M. Turner since I found them definitely interesting.

Tropical rainforests are the most species rich terrestrial ecosystems especially in terms of vascular plants: vascular plants species richness in tropical rainforests amounts to more than half of the estimated total. Let’s wonder why?

Biological diversity is the balance between speciation and extinction processes. Therefore these ecosystems should be characterized by more rapid speciation and/or a slower rate of extinction. It is possible that the benign and equable climate of the tropics makes it less likely that a species will become extinct.

From an ecological perspective species occupying separate niches have reached a competitive equilibrium that allows numerous species to co-occur. However if we think about plants simple requirements (light, water, nutrients) it is difficult to imagine a number of niches comparable to the number of species occurring in tropical rainforests, even if we take into account reproduction and regeneration requirements. It is more plausible that ecologically similar species can co-occur.

If competitive equilibrium has not been obtained then something must be preventing competitive exclusion. One possible process by which this could happen is through frequency-dependent mortality, setting an upper limit on the abundance of a species and thus making it unlikely that it can totally exclude other species from the landscape (see Janzen-Connel effect for an in-depth description of this process).

This compensatory mortality, often due to seed and seedling predators and pests and pathogens may increase in intensity with rainfall bacause pest and pathogens populations are more spread in an ever-wet forest.

Another view recalls the fact that most species are so infrequent that very rarely come into direct competition with other ecologically similar sparse species. Therefore many potential episodes of interspecific competition may be won by default because no adversaries were present at the right time and place.

At present we have no simple answer to the title’s question, nor does it seems likely that there is a simple answer. Probably all the factors mentioned  and possibly others not yet considered are operating within any rainforest.

Response and effect

Among plant functional traits it is now widely accepted to distinguish response and effect traits.

Response traits are those associated to plant response to environmental factors.

Effect traits are those related to the plant effects on ecosystem functioning.

The first group of traits affect the resilience of an ecosystem; the second determine the effects of plants on ecosystem functions such as biogeochemical processes, CO2 fixation, productivity, etc.

In fact, it was postulated that functional effect groups (species with a similar effect on one or several ecosystem functions; e.g., primary productivity, nutrient cycling) and functional response groups (groups of species with a similar response to a particular environmental factor; e.g., resource availability, disturbance or CO2) do not necessarily coincide (chapter 13 in Canadell et al. 2007).

The separation among response and effect traits used in a recent paper on this topic (see Laliberté et al., 2010 on Ecology Letters). In it the functional redundancy of each effect group per each stand is calculated as the richness of functionally similar species in each effect group. For each functional effect group, we the response diversity is then calculated by means of the functional dispersion index described by Laliberte & Legendre (2010 in Ecology).

Functional response diversity ensures that an ecosystem is able to respond to disturbance events in different ways, therefore that its resilience is high. Effect redundancy on the other hand ensures that although the extinction of one species other species will be able to “keep the ecosystem functioning”.

Therefore this method allows to evaluate the ecosystem resilience diversity for each group of species providing a similar “service”.

I think this approach should be applied estensively as it seems able to relate biodiversity and ecosystem functioning in a great way, giving an answer to a topical issue.

E-taxonomy

Global Biodiversity Information Facility

This site includes a great data portal, e.g. you can browse it by species and see a list of the matching records in a table or in a map, be redirected to the source that sometimes shows also images of the species. All the kingdoms are included in the portal.

Enjoy!

About e-taxonomy you can also read this.

Biodiversity Heritage Library

Biodiversity Heritage Library

Scientific literature started far before .pdf files.

Nowadays the less recent “paper” publications are perceived as more difficult to access even if they didn’t move at all, only because the newest publications are much easier to find. This is leading to pay less attention to the literature legacy.

This process is particularly worrying in relation to legacy taxonomic literature, that is of exceptional value because the domain of systematic biology depends — more than any other science — upon historic literature.

Biodiversity conservation strongly depends on the knowledge of biological diversity, therefore on the conservation of the publications on systematic biology. This problem is particularly acute for the developing countries that are home to the majority of the world’s biodiversity.

This is why I found absolutely interesting the linked site, it is easy to search for any species for which you can then browse an incredible literature. Enjoy!

A must see

The entire documentary deserves your time!

Forests in Sabina

Part of the town of  Roccantica

Sabini Mts. are about 60 km from Rome. If you leave the olive groves and start to walk up the mountain near the cute town of Roccantica one of your possibilities is to head Monte Pizzuto. It’s a walk across evergreen oak (Quercus ilex) forests so spread in this region and usually managed as coppices.

Elm oak coppice

Anyway, going up you will cross also deciduous oaks stands (Quercus pubescens s.l.) on the sunny slopes and maples (Acer obtusatum) in the patches where morphology allows for more mesic species to occur. The beech forest start rather abruptly while you keep walking up.

Hepatica nobilis,  one of the earliet flowers of beech forests

Hepatica  nobilis,  one of the earliet flowers of beech forests

Elm oak is very competitive on cliffs insomuch as even at altitudes where beech dominates, on the cliffs elm oak is the only species occurring. Its preference for shallow soils makes rather likely that also at lower altitudes the occurrence of elm oaks rather than of deciduous oaks may be related to past human activities that caused soil erosion. Maybe if these forests won’t be managed anymore deciduous oaks would gradually become more and more frequent in them to the detritent of elm oak forests.

Who wins?

Saving forests, cultures and carbon dioxide – “Win-win’ conservation should start with indigenous lands and other protected areas”

Is it better to fund project directed towards the local communities, indigenous people and forests which relate to reducing emission from deforestation and forest degradation through REDD-plus mechanisms or to establish new Indigenous Lands and other Protected Areas (ILPA’s)?

The latter choice is defined as a win-win strategy as “per ton of carbon dioxide equivalent the costs of protected areas establishment and management amounts to roughly 9–13 percent of the capital that could be generated by REDD-plus at a conservative price of US$5 per ton of carbon dioxide equivalent”.

But what is a carbon saving? An area saved from a potential deforestation or a protected area that will not be deforested anyway since its establishment? “Why would wealthy governments pay for what the developing countries have already committed to?”

It’s incredible how complex it is to assess the effectiveness of policies to avoid deforestation especially in developing countries…as the debate goes on…who is winning?