Bernice Hwang
Doctoral student
Impacts and drivers of insect herbivory on element cycling in forests globally
Author
Summary, in English
I found substantial evidence for a wide variety of important interactions between plant Si and herbivory but highlight the need for more research particularly in non-graminoid-dominated vegetation outside of the temperate biome as well as on the potential effects of herbivory on Si cycling. The global mean for net insect-mediated N flux was approximately 25% of the global mean for atmospheric N deposition. The global mean for net insect-mediated P flux was 280% that of the global mean for atmospheric P deposition and 0.03% of the global mean for mineral weathered P. However, insect-mediated element fluxes represented a larger proportion of total N and P deposition in the tropical region than in temperate or boreal regions, which could have large implications for forests in P-limited areas such as the Tropics. Overall, insect folivores liberated greater amounts of studied elements from the canopy in warmer and drier sites than cooler and wetter sites globally, but trends at local scales did not always reflect global patterns. In addition, insect-mediated element fluxes were most affected by mean annual temperature (MAT) and mean annual precipitation (MAP) globally. Foliar production and leaf-level herbivory rate explained the most variability in insect-mediated element fluxes. In turn, foliar production and to a lesser extent leaf-level herbivory and foliar nutrient concentrations were largely driven by MAT. The litter decomposition study also demonstrated that increased MAT and insect inputs additively increased litter decomposition and N immobilization rates, with effects being stronger for litterbags amended with the highest, outbreak-level amount of insect inputs.
The findings from this thesis highlight that relatively small but chronic and labile forms of nutrients from herbivory by insects at low densities could affect long-term ecosystem C and nutrient cycling as much or more than episodic outbreak events. Climate change in broadleaf forests can have important but variable impacts on productivity and insect herbivory rates, with consequences for soil fertility and ecosystem processes, but the magnitude and direction of these impacts will depend on climate variable, foliar element and spatio-temporal scale.
Department/s
- Dept of Physical Geography and Ecosystem Science
- MERGE: ModElling the Regional and Global Earth system
Publishing year
2022-10-13
Language
English
Full text
- Available as PDF - 95 kB
- Available as PDF - 1 MB
- Download statistics
Document type
Dissertation
Publisher
Lund University
Topic
- Ecology
Keywords
- biogeochemical cycling
- folivory
- insect cadavers
- insect frass
- insect herbivory
- litter decomposition
- nutrient cycling
- carbon
- nitrogen
- phosphorus
- silicon
- silica
Status
Published
Supervisor
- Daniel Metcalfe
ISBN/ISSN/Other
- ISBN: 978-91-89187-17-7
- ISBN: 978-91-89187-18-4
Defence date
18 November 2022
Defence time
13:00
Defence place
Världen (Sal F111), Geocentrum I. Join via zoom: https://lu-se.zoom.us/j/64966653510?pwd=cTlIOW40UWZjS3hVYXJJQ3YzbS9nUT09
Opponent
- Richard Lindroth (Professor)