spatiotemporal effects of climate on the relationship between tree diversity and forest ecosystem functioning
abstract
worldwide, forest ecosystem functioning and plant diversity have been altered by global
environmental change. understanding the relationship between biodiversity and ecosystem
functioning with long-term environmental change is important because maintaining
diversity can mitigate the impacts of environmental change on ecosystem functioning.
here, i i) developed a concept that can elucidate how enhancing plant diversity may help
mitigate global environmental change impacts on ecosystem functioning; ii) empirically
tested this concept in natural forest systems by examining whether higher tree diversity
enhances and reduces positive and negative impacts of long-term environmental change on
forest biomass dynamics (biomass growth, loss, and net biomass change); iii) explored
effects of spatial variations in climate on the relationship between tree functional diversity
and forest biomass dynamics; and iv) investigated how spatial variations in climate mediate
the impacts of long-term environmental change on tree functional composition.
in order to establish the concept of how tree diversity can mitigate the impacts of
global environmental change on forest ecosystem functioning, i reviewed the field of
climate change effects on biodiversity-ecosystem functioning. i found mixed evidence for
positive diversity effects on ecosystem functioning persistent before and after experiencing
changes in climates within grassland communities, but strong support in the few studies
conducted in forest ecosystems which are more stable and resilient at higher levels of
diversity. i identify the importance of future research combining investigations into climate
change impacts on ecosystem functionality with the b-ef. i concluded that biodiversity can
hold certain potential to be a solution to mitigate environmental change impacts.
using inventory data of boreal forests of western canada from 1958-2011, i
revealed that aboveground biomass growth of species-rich forests increased with the
calendar year but that of species-poor forests decreased. moreover, species-rich forests
experienced less aboveground biomass loss from tree mortality than species-poor forests. i
found that the growth of species-rich forests, but not species-poor forests, was positively
associated with elevated co2. mortality in species-poor forests increased more with
decreasing water availability than species-rich forests. in contrast, growth decreased, and
mortality increased as the climate warmed regardless of species diversity. the results of
this study suggest that promoting high tree diversity may help reduce the climate and
environmental change vulnerability of boreal forests.