The most unique feature of Earth is the existence of life, and the most extraordinary feature of life is its diversity. Approximately 9 million types of plants, animals, protists and fungi inhabit the Earth. So, too, do 7 billion people. Two decades ago, at the first Earth Summit, the vast majority of the world's nations declared that human actions were dismantling the Earth's ecosystems, eliminating genes, species and biological traits at an alarming rate. This observation led to the question of how such loss of biological diversity will alter the functioning of ecosystems and their ability to provide society with the goods and services needed to prosper.

/pdf/biodiversity-loss-and-its-impact-on-humanity-2d0fgc88mg.pdf

Biodiversity loss and its impact on humanity

Plant functional traits are the features (morphological, physiological, phenological) that represent ecological strategies and determine how plants respond to environmental factors, affect other trophic levels and influence ecosystem properties. Variation in plant functional traits, and trait syndromes, has proven useful for tackling many important ecological questions at a range of scales, giving rise to a demand for standardised ways to measure ecologically meaningful plant traits. This line of research has been among the most fruitful avenues for understanding ecological and evolutionary patterns and processes. It also has the potential both to build a predictive set of local, regional and global relationships between plants and environment and to quantify a wide range of natural and human-driven processes, including changes in biodiversity, the impacts of species invasions, alterations in biogeochemical processes and vegetation–atmosphere interactions. The importance of these topics dictates the urgent need for more and better data, and increases the value of standardised protocols for quantifying trait variation of different species, in particular for traits with power to predict plant- and ecosystem-level processes, and for traits that can be measured relatively easily. Updated and expanded from the widely used previous version, this handbook retains the focus on clearly presented, widely applicable, step-by-step recipes, with a minimum of text on theory, and not only includes updated methods for the traits previously covered, but also introduces many new protocols for further traits. This new handbook has a better balance between whole-plant traits, leaf traits, root and stem traits and regenerative traits, and puts particular emphasis on traits important for predicting species’ effects on key ecosystem properties. We hope this new handbook becomes a standard companion in local and global efforts to learn about the responses and impacts of different plant species with respect to environmental changes in the present, past and future.

/pdf/new-handbook-for-standardised-measurement-of-plant-5aljxhhg5y.pdf

New handbook for standardised measurement of plant functional traits worldwide

Human activities, especially conversion and degradation of habitats, are causing global biodiversity declines. How local ecological assemblages are responding is less clear--a concern given their importance for many ecosystem functions and services. We analysed a terrestrial assemblage database of unprecedented geographic and taxonomic coverage to quantify local biodiversity responses to land use and related changes. Here we show that in the worst-affected habitats, these pressures reduce within-sample species richness by an average of 76.5%, total abundance by 39.5% and rarefaction-based richness by 40.3%. We estimate that, globally, these pressures have already slightly reduced average within-sample richness (by 13.6%), total abundance (10.7%) and rarefaction-based richness (8.1%), with changes showing marked spatial variation. Rapid further losses are predicted under a business-as-usual land-use scenario; within-sample richness is projected to fall by a further 3.4% globally by 2100, with losses concentrated in biodiverse but economically poor countries. Strong mitigation can deliver much more positive biodiversity changes (up to a 1.9% average increase) that are less strongly related to countries' socioeconomic status.

/pdf/global-effects-of-land-use-on-local-terrestrial-biodiversity-31yzxze5ly.pdf

Global effects of land use on local terrestrial biodiversity

Summary 1. The leaf economics spectrum (LES) provides a useful framework for examining species strategies as shaped by their evolutionary history. However, that spectrum, as originally described, involved only two key resources (carbon and nutrients) and one of three economically important plant organs. Herein, I evaluate whether the economics spectrum idea can be broadly extended to water – the third key resource –stems, roots and entire plants and to individual, community and ecosystem scales. My overarching hypothesis is that strong selection along trait trade-off axes, in tandem with biophysical constraints, results in convergence for any taxon on a uniformly fast, medium or slow strategy (i.e. rates of resource acquisition and processing) for all organs and all resources. 2. Evidence for economic trait spectra exists for stems and roots as well as leaves, and for traits related to water as well as carbon and nutrients. These apply generally within and across scales (within and across communities, climate zones, biomes and lineages). 3. There are linkages across organs and coupling among resources, resulting in an integrated whole-plant economics spectrum. Species capable of moving water rapidly have low tissue density, short tissue life span and high rates of resource acquisition and flux at organ and individual scales. The reverse is true for species with the slow strategy. Different traits may be important in different conditions, but as being fast in one respect generally requires being fast in others, being fast or slow is a general feature of species. 4. Economic traits influence performance and fitness consistent with trait-based theory about underlying adaptive mechanisms. Traits help explain differences in growth and survival across resource gradients and thus help explain the distribution of species and the assembly of communities across light, water and nutrient gradients. Traits scale up – fast traits are associated with faster rates of ecosystem processes such as decomposition or primary productivity, and slow traits with slow process rates. 5. Synthesis. Traits matter. A single ‘fast–slow’ plant economics spectrum that integrates across leaves, stems and roots is a key feature of the plant universe and helps to explain individual ecological strategies, community assembly processes and the functioning of ecosystems.

/pdf/the-world-wide-fast-slow-plant-economics-spectrum-a-traits-2qqc6fx0m7.pdf

The world‐wide ‘fast–slow’ plant economics spectrum: a traits manifesto

The authors found that the key elements of plant form and function, analysed at global scale, are largely concentrated into a two-dimensional plane indexed by the size of whole plants and organs on the one hand, and the construction costs for photosynthetic leaf area, on the other.

The global spectrum of plant form and function

The Cretaceous/Tertiary boundary extinction has long been considered one of the most important identifiable events in the course of Phanerozoic evolution. At times, the dramatic evidence for this has obscured the fact that any extinction event is selective and may not affect all groups of organisms in the same way. In this paper we examine a North American plant fossil database from the Mesozoic and Cenozoic eras in order to re-evaluate the evolutionary significance of the Cretaceous/Tertiary extinction on plants. When we compare the leaf architectural profiles of fossil floras in each stage of the Cretaceous and epoch of the Cenozoic, we find that the changes in leaf architecture at the Maastrichtian/Paleocene boundary cannot be statistically distinguished from the population of changes at other boundaries. To the extent that patterns in leaf architecture reflect ecosystem structure, we can therefore conclude that despite the local species or morphotype extinctions that are known to have taken place at the boundary, the effect of the extinction on the structure of plant ecosystems was either minor or short-lived. Certainly, the extinction seems insignificant compared with the dramatic changes in leaf architecture that accompanied the rise of angiosperms in the middle Cretaceous. This analysis also provides an example of the importance of time scales in the evaluation of macro-evolutionary pattern, and shows how the use of morphological categories instead of phylogenetic groups or simple diversity measures can produce rich and ecologically informative semi-quantitative proxy measurements of plant evolutionary patterns.

Leaf architectural profiles of angiosperm floras across the Cretaceous/Tertiary boundary

CO2 starvation experiments provide support for the carbon-limited hypothesis on the evolution of CAM-like behaviour in Isoëtes

1 National Museum of Natural History, Smithsonian Institution, Washington, DC 20013 USA 2 Department of Geology, Baylor University, One Bear Place #97354, Waco, TX 76798 USA 3 Harvard University Botanical Museum, 26 Oxford Street, Cambridge, MA 02138 USA 4 Corresponding author: Department of Biology, Indiana University Southeast, 4201 Grant Line Road, New Albany, IN 47150 USA —email: dwtaylo2@ius.edu

https://bioone.org/journals/Bulletin-of-the-Peabody-Museum-of-Natural-History/volume-55/issue-2/014.055.0201/The-Multi-Stranded-Career-of-Leo-J-Hickey/10.3374/014.055.0201.pdf

The Multi-Stranded Career of Leo J. Hickey

Metabolic shifts play an essential role in the survival of plants in extreme habitats. Certain desert plant species, for example, avoid water loss by temporally segregating the light and dark reactions of photosynthesis. By only opening their stomata at night these plants inhibit significant water loss during the day. At night CO2 is incorporate into 4-carbon acids for subsequent daytime fixation1-5. This behavior is known as Crassulacean Acid Metabolism (CAM) and leads to noticeable diel cycles in pH of photosynthetic organs1-5. Oddly, similar acidity cycles are found in the submerged aquatic lycophyte genus Isoetes2,6-12, which are not water limited in any sense. It has long been assumed that their nocturnal CO2 accumulation is an adaptation to low daytime carbon levels in aquatic ecosystems, but this has never been empirically tested2,6-13. Here, we offer direct evidence that CO2 starvation induces CAM-like nocturnal carbon accumulation in terrestrial Isoetes. Populations of terrestrial Isoetes engelmannii grown in climate-controlled chambers and starved of atmospheric CO2 during the day displayed diel acidity cycles similar to those in both xerophytic CAM plants and submerged Isoetes species. These results substantiate the hypothesis that carbon starvation provides a selective pressure for nocturnal carbon accumulation in Isoetes. Furthermore, while aquatic CO2 levels undoubtedly promote nocturnal carbon accumulation in extant Isoetes, the induction of this behavior in terrestrial plants suggests a possible earlier terrestrial evolution of this metabolism in response to low atmospheric CO2 levels during the Carboniferous period14-17. Our findings therefore both provide empirical support for a long-standing assumption about nocturnal carbon accumulation in the lycophyte lineage2,6-12,18 and suggest an earlier evolution of this behavior, leading to the notion that CAM in xerophytes may only represent a subset of metabolisms that employ nocturnal carbon accumulation in response to variable environmental pressures.

/pdf/low-atmospheric-co2-induces-nocturnal-carbon-accumulation-in-4tlikgx1jq.pdf

Walton A. Green

Papers

Leaf architectural profiles of angiosperm floras across the Cretaceous/Tertiary boundary

CO2 starvation experiments provide support for the carbon-limited hypothesis on the evolution of CAM-like behaviour in Isoëtes

The Multi-Stranded Career of Leo J. Hickey

Low atmospheric CO2 induces nocturnal carbon accumulation in the lycophyte genus Isoetes