Nathalie Butt

Scale‐dependent relationships between tree species richness and ecosystem function in forests

1. The relationship between species richness and ecosystem function, as measured by productivity or biomass, is of long-standing theoretical and practical interest in ecology. This is especially true for forests, which represent a majority of global biomass, productivity and biodiversity.

Evidence that deforestation affects the onset of the rainy season in Rondonia, Brazil

[1] Anecdotes from local residents and modeling studies suggest that deforestation may delay the onset of the rainy season (O) in western Brazil, but detection studies using climatological time series are not available. Here we investigate trends in O in the state of Rondonia, Brazil, a region that has been continuously deforested since the 1970s. Daily rainfall data from 16 station time series, spanning periods of at least 25 years, with five covering more than 30 years, are used. We define O as the first day after 1 September with rainfall greater than 20 mm d −1 .A t test indicates that for stations that lie inside the major deforestedarea,Ohassignificantlyshiftedto,onaverage,11days(andupto18days)laterin the year over the last three decades. However, for stations that lie in areas that have not been heavily deforested, O has not shifted significantly. Nonparametric and parametric trend analyses all gave similar results for the change of O with time, and all of the statistically significant results indicated a delay in O. Twenty‐five percent (four) of the stations analyzed showed a marked shift in timing of O: these stations are located inside deforested areas, primarily near the BR 364 highway that crosses Rondonia. Delayed onset may be a result of land use change, and this signal may strengthen in future: current delaying trends may be as great as 0.6 days per year, and after 30 years of deforestation the onset of the rainy season is expected to be 18 days later.

The sensitivity and vulnerability of terrestrial habitats and species in Britain and Ireland to climate change.

Abstract Climate change is having an increasing impact on the distribution and functioning of species and habitats. This has important implications for conservation practice and policy. The aim of this study was to model the direct impacts of climate change on terrestrial environments in Britain and Ireland in order to understand the possible changes in the distribution of species and the composition of habitats. A model, based on an artificial neural network, was used to predict changes in the bioclimate envelope of species, under the UKCIP98 climate change scenarios. A total of 50 species, representing several taxa, were modelled. Many species demonstrated a consistent response to climate change, either increasing or losing suitable climate space, although some had a variable response with losses starting to occur under the high scenarios. The percentage change in the bioclimate envelope of the species was calculated. This showed that montane species and habitats were the most sensitive to climate change. Other habitats from upland areas or species with northern distributions were also sensitive to losses, while species gaining suitable climate space represented a variety of habitats. Sensitivity needs to be viewed alongside vulnerability, the ability of the species or habitat to adapt to climate change. Montane species and habitats were the most vulnerable, with limited adaptation possibilities. Other vulnerable habitats, for which species modelling was carried out, include lowland raised bog, lowland calcareous grassland and native pine woodland. The potential impacts of climate change should be taken into account when planning conservation measures for these sensitive and vulnerable species and habitats.

Biodiversity Risks from Fossil Fuel Extraction

The overlapping of biodiverse areas and fossil fuel reserves indicates high-risk regions. Despite a global political commitment to reduce biodiversity loss by 2010 through the 2002 Convention on Biological Diversity, declines are accelerating and threats are increasing (1). Major threats to biodiversity are habitat loss, invasion by exotic species and pathogens, and climate change, all principally driven by human activities. Although fossil fuel (FF) extraction has traditionally been seen as a temporary and spatially limited perturbation to ecosystems (2), even local or limited biodiversity loss can have large cascade effects on ecosystem function and productivity. We explore the overlap between regions of high marine and terrestrial biodiversity and FF reserves to identify regions at particular risk of ecosystem destruction and biodiversity loss from exposure to FF extraction.

Fires increase Amazon forest productivity through increases in diffuse radiation

Atmospheric aerosol scatters solar radiation increasing the fraction of diffuse radiation and the efficiency of photosynthesis. We quantify the impacts of biomass burning aerosol (BBA) on diffuse radiation and plant photosynthesis across Amazonia during 1998–2007. Evaluation against observed aerosol optical depth allows us to provide lower and upper BBA emissions estimates. BBA increases Amazon basin annual mean diffuse radiation by 3.4–6.8% and net primary production (NPP) by 1.4–2.8%, with quoted ranges driven by uncertainty in BBA emissions. The enhancement of Amazon basin NPP by 78–156 Tg C a−1 is equivalent to 33–65% of the annual regional carbon emissions from biomass burning. This NPP increase occurs during the dry season and acts to counteract some of the observed effect of drought on tropical production. We estimate that 30–60 Tg C a−1 of this NPP enhancement is within woody tissue, accounting for 8–16% of the observed carbon sink across mature Amazonian forests.

Cascading effects of climate extremes on vertebrate fauna through changes to low-latitude tree flowering and fruiting phenology.

Forest vertebrate fauna provide critical services, such as pollination and seed dispersal, which underpin functional and resilient ecosystems. In turn, many of these fauna are dependent on the flowering phenology of the plant species of such ecosystems. The impact of changes in climate, including climate extremes, on the interaction between these fauna and flora has not been identified or elucidated, yet influences on flowering phenology are already evident. These changes are well documented in the mid to high latitudes. However, there is emerging evidence that the flowering phenology, nectar/pollen production, and fruit production of long-lived trees in tropical and subtropical forests are also being impacted by changes in the frequency and severity of climate extremes. Here, we examine the implications of these changes for vertebrate fauna dependent on these resources. We review the literature to establish evidence for links between climate extremes and flowering phenology, elucidating the nature of relationships between different vertebrate taxa and flowering regimes. We combine this information with climate change projections to postulate about the likely impacts on nectar, pollen and fruit resource availability and the consequences for dependent vertebrate fauna. The most recent climate projections show that the frequency and intensity of climate extremes will increase during the 21st century. These changes are likely to significantly alter mass flowering and fruiting events in the tropics and subtropics, which are frequently cued by climate extremes, such as intensive rainfall events or rapid temperature shifts. We find that in these systems the abundance and duration of resource availability for vertebrate fauna is likely to fluctuate, and the time intervals between episodes of high resource availability to increase. The combined impact of these changes has the potential to result in cascading effects on ecosystems through changes in pollinator and seed dispersal ecology, and demands a focused research effort.

A call for inclusive conservation

Heather Tallis, Jane Lubchenco and 238 co-signatories petition for an end to the infighting that is stalling progress in protecting the planet.

Increasing elevation of fire in the Sierra Nevada and implications for forest change

Fire in high-elevation forest ecosystems can have severe impacts on forest structure, function and biodiversity. Using a 105-year data set, we found increasing elevation extent of fires in the Sierra Nevada, and pose five hypotheses to explain this pattern. Beyond the recognized pattern of increasing fire frequency in the Sierra Nevada since the late 20th century, we find that the upper elevation extent of those fires has also been increasing. Factors such as fire season climate and fuel build up are recognized potential drivers of changes in fire regimes. Patterns of warming climate and increasing stand density are consistent with both the direction and magnitude of increasing elevation of wildfire. Reduction in high elevation wildfire suppression and increasing ignition frequencies may also contribute to the observed pattern. Historical biases in fire reporting are recognized, but not likely to explain the observed patterns. The four plausible mechanistic hypotheses (changes in fire management, climate, fuels, ignitions) are not mutually exclusive, and likely have synergistic interactions that may explain the observed changes. Irrespective of mechanism, the observed pattern of increasing occurrence of fire in these subalpine forests may have significant impacts on their resilience to changing climatic conditions.

Spatial patterns and recent trends in cloud fraction and cloud‐related diffuse radiation in Amazonia

declined at a rate of 0.3% yr � 1 , and the wet season decline was 0.1% yr � 1 . In the west of the region a 1% increase in CRDRP is indicated. Changes in forest composition and productivity may be linked to changes in CRDRP in that decreases in cloud cover in sunny regions or dry seasons may cause a decline in productivity, whereas declines in cloud cover in cloudy regions, or during cloudy seasons, may cause an increase in productivity.

Shifting dynamics of climate-functional groups in old-growth Amazonian forests

Background: Climate change is driving ecosystem shifts, which has implications for tropical forest system function and productivity. Aim: To investigate Amazon forest dynamics and test for compositional changes between 1985 and 2005 across different plant groups. Methods: Tree census data from 46 long-term RAINFOR forest plots in Amazonia for three climate-functional groups were used: dry-affiliate, climate-generalist and wet affiliate. Membership of each group was ascribed at genus level from the distribution of individuals across a wet–dry gradient in Amazonia, and then used to determine whether the proportions of these functional groups have changed over time, and the direction of any change. Results: In total, 91 genera, representing 59% of the stems and 18% of genera in the plots, were analysed. Wet-affiliates tended to move from a state of net basal area gain towards dynamic equilibrium, defined as where gain ≈ loss, governed by an increase in loss rather than a decrease in growth and mainly driven by plots in north-west Amazonia, the wettest part of the region. Dry-affiliates remained in a state of strong net basal area gain across western Amazonia and showed a strong increase in stem recruitment. Wet-affiliates and climate-generalists showed increases in stem mortality, and climate-generalists showed increased stem recruitment, resulting in overall equilibrium of stem numbers. Conclusions: While there were no significant shifts in most genera, the results suggest an overall shift in climate-functional forest composition in western Amazonia away from wet-affiliates, and potential for increased forest persistence under projected drier conditions in the future.