Cecropia peltata (trumpet tree).

C. peltata is an important pioneer species in its native range Americas following forest clearance. It has also been introduced into coffee plantations as a shade tree and into botanical gardens in Africa. However, its presence on the ISSG list of the 100 worst invasive species (ISSG, 2003) means that its notoriety as an invasive species may limit further introductions.

Ambrosia peruviana (Peruvian ragweed).

Ambrosia peruviana is a short-lived perennial herb native to Central and South America. It is a common weed of pastures, disturbed sites, roadsides and riverbanks. It is also culivated as an ornamental and medicinal herb. Its tendency to grow in isolated clusters amid other vegetation suggested that the plant may possess allelopathic activity, a trait previously reported for other members of the genus. As A. peruviana is fast-growing it has the potential to displace native vegetation in its introduced range, especially after a disturbance such as overgrazing, forest clearance or construction.

Long-term (1990-2019) monitoring of tropical moist forests dynamics

ABSTRACTAccurate characterization of the tropical moist forests changes is needed to support conservation policies and to better quantify their contribution to global carbon fluxes. We document - at pantropical scale - the extent of these forests and their changes (degradation, deforestation and recovery) over the last three decades. We estimate that 17% of the tropical moist forests have disappeared since 1990 with a remaining area of 1060 million ha in 2019, from which 8.5% are degraded. Our study underlines the importance of the degradation process in such ecosystems, in particular as precursor of deforestation and in the recent increase of the tropical moist forest disturbances. Without reduction of the present disturbance rates, undisturbed forests will disappear entirely in large tropical humid regions by 2050. Our study suggests reinforcing actions to prevent the first disturbance scar that leads to forest clearance in 45% of the cases.

How do tropical peatland greenhouse gas emissions respond in the immediate aftermath of a fire?

<p>Southeast Asia is a region where forest clearance, drainage of peatlands for agriculture, and ongoing use of fire to ‘manage’ land leads to extensive emissions of greenhouse gases to the atmosphere, and significant disturbance to peatland soils. While recent campaigns investigating tropical peatland fire emissions have improved our knowledge and understanding of ‘direct’ greenhouse gas emissions during fires, there remains a significant gap in our knowledge of the immediate post-fire impacts on peat respiration and methanogenesis. Ongoing research shows that peatland microbial communities (responsible for respiration), including methanogens and methanotrophs (responsible for controlling net methane emissions), are considerably altered following fire disturbance. As such, we hypothesise that peatland fires will lead to significant alterations to GHG emissions, compared to sites that have not burned. Further, we also hypothesise that the magnitude of this post-fire effect will be predictably interrelated to different forms of peatland degradation and land-use history.</p><p>Here we present results from seven fire locations (recently burnt) and their corresponding neighbouring control sites (not recently burnt), three of our fire locations were associated with forest clearance fires, while the other four locations were slash fires on oil palm plantations. We characterize the post-fire disturbance emissions of carbon dioxide (CO<sub>2</sub>) and methane (CH<sub>4</sub>) in situ, in the immediate aftermath of a fire (within days or weeks), and in the subsequent months following a fire at our burn sites. For comparison, we also measure CO<sub>2</sub> and CH<sub>4</sub> emissions from neighbouring control sites that remained unburnt. We find substantial, significant differences in CH<sub>4</sub> emissions between the burn sites and control sites for all seven of our measurement locations. We suggest a number of mechanisms responsible for this post-fire effect, including disturbance to the methanotroph microbial communities at the burn sites, as well as reduced elevation at the burn sites, leading to higher water tables.</p>