Photosynthetic temperature responses of tree species in Rwanda: evidence of pronounced negative effects of high temperature in montane rainforest climax species.

The sensitivity of photosynthetic metabolism to temperature has been identified as a key uncertainty for projecting the magnitude of the terrestrial feedback on future climate change. While temperature responses of photosynthetic capacities have been comparatively well investigated in temperate species, the responses of tropical tree species remain unexplored. We compared the responses of seedlings of native cold-adapted tropical montane rainforest tree species with those of exotic warm-adapted plantation species, all growing in an intermediate temperature common garden in Rwanda. Leaf gas exchange responses to carbon dioxide (CO2 ) at different temperatures (20-40°C) were used to assess the temperature responses of biochemical photosynthetic capacities. Analyses revealed a lower optimum temperature for photosynthetic electron transport rates than for Rubisco carboxylation rates, along with lower electron transport optima in the native cold-adapted than in the exotic warm-adapted species. The photosynthetic optimum temperatures were generally exceeded by daytime peak leaf temperatures, in particular in the native montane rainforest climax species. This study thus provides evidence of pronounced negative effects of high temperature in tropical trees and indicates high susceptibility of montane rainforest climax species to future global warming.

Thermal Profiles of Chainsaw Hollows and Natural Hollows during Extreme Heat Events.

Loss of hollow-bearing trees threatens many hollow-dependent wildlife. To mitigate this process, artificial chainsaw-carved hollows (CHs) are often created in dead trees, yet little is known about their thermal profiles. We measured temperatures inside 13 natural hollows (8 live and 5 dead trees) and 45 CHs (5 live and 40 dead trees) in the central west of NSW, Australia, over the course of 2 summers. Maximum temperatures and daily temperature ranges within natural hollows and artificial hollows were similar in 2017-2018. Hollow temperatures were lower in thicker-walled hollows than in thinner-walled hollows. During the January 2019 heatwave, temperatures inside CHs in dead trees exceeded 4-35 °C higher than the upper limit of the thermal neutral zone of sugar gliders-for 6.2 consecutive days (range 0-9 days). CHs in dead trees provided little buffering from thermal extremes; when air temperatures peaked at 44.6 °C, CHs in dead trees were on average 2.4 °C cooler than ambient (range: 5.5 °C cooler to 1.0 °C hotter than ambient). These results show that CHs created in dead trees may not provide suitable thermal conditions for hollow-dependent marsupials during summer heatwaves. Retention of large live trees, coupled with revegetation, is crucial for conserving hollow-dependent fauna in agricultural landscapes.

Monitoring techniques of the western corn rootworm are the precursor to effective IPM strategies.

BACKGROUND: The western corn rootworm (WCR) is economically the most important pest of maize in Croatia. To predict WCR adult population abundance and variability, traditional, genetic and morphometric monitoring of populations was conducted over time through each phase of the WCR invasion process in Croatia. RESULTS: Through traditional monitoring it was shown that WCR established their current population and reached economic densities after 14 years persisting in the study area. Regression-tree-based modelling showed that the best predictor of WCR adult abundance was the total amount of rainfall. Genetic monitoring indicated that genetic differentiation increased over time at the intrapopulation level, and morphometric monitoring indicated that wing morphotypes varied according to edaphic landscape changes. CONCLUSION: Traditional population metric surveys are important in WCR integrated pest management (IPM), as such surveys can be effectively used to predict population abundances. Novel-use monitoring techniques such as genetics and geometric morphometrics can be used to provide valuable information on variation within and among populations. The monitoring techniques presented herein provide sound data to assist in the understanding of both WCR ecology and population genetics and may provide more information than that currently available using traditional techniques (e.g. sticky traps), and as such these additional techniques should be written into IPM for WCR.

Mammalian hair as an accumulative bioindicator of metal bioavailability in Australian terrestrial environments.

The current study represents the first investigation of the suitability of marsupial and eutherian mammalian hair as indicator tissue for metal exposure and accumulation within contaminated Australian terrestrial ecosystems. A soil metal contamination gradient was established across 22 sites at increasing distances from a decommissioned Lead/Zinc smelter in NSW, Australia. Within each site, soil and small mammal populations were sampled. An Australian native marsupial, the insectivorous Brown Antechinus, Antechinus stuartii: Dasyuridae, and introduced rodents, the omnivorous Brown or Norway Rat, Rattus norvegicus: Muridae and the Black Rat, Rattus rattus: Muridae were assessed for hair concentrations of Cadmium (Cd), Copper (Cu), Lead (Pb) and Zinc (Zn). Metals in soil were most elevated at sites within close proximity to the smelter, with soil metal concentrations decreasing with distance from the smelter. The non-essential metals Pb and Cd were accumulated in hair, both metals exhibiting positive linear relationships with environmental exposure (soil metal concentrations). When the variables of weight and snout-vent length were considered, no further contribution in terms of explaining the variability in hair Cd or Pb was observed for all species examined. The essential metals Cu and Zn were regulated in hair, remaining similar across the metal contamination gradient. A significant negative correlation between snout-vent length and hair Cu concentration was found for the Brown Rat; greater hair Cu concentrations were found in smaller individuals of this species. Accumulation of Pb to hair was similar among species while concentrations of Cd in Brown Rat hair were higher than both Black Rat and Brown Antechinus hair. As each of the three aforementioned species exhibit similar bioaccumulation relationships for Pb, we suggest that sampling hair from introduced rodents (pest species) may provide a suitable proxy for the assessment of Pb bioavailability for a range of small mammals within Australian urban remnants.