TY - JOUR
T1 - Bottom-up and top-down effects on plant communities
T2 - nutrients limit productivity, but insects determine diversity and composition
AU - Souza, Lara
AU - Zelikova, Tamara Jane
AU - Sanders, Nate
PY - 2016/4/1
Y1 - 2016/4/1
N2 - Top-down effects of herbivores and bottom-up effects of nutrients shape productivity and diversity across ecosystems, yet their single and combined effects on spatial and temporal beta diversity is unknown. We established a field experiment in which the abundance of insect herbivores (top-down) and soil nitrogen (bottom-up) were manipulated over six years in an existing old-field community. We tracked plant α and β diversity - within plot richness and among plot biodiversity- and aboveground net primary productivity (ANPP) over the course of the experiment. We found that bottom-up factors affected ANPP while top-down factors influenced plant community structure. Across years, while N reduction lowered ANPP by 10%, N reduction did not alter ANPP relative to control plots. Further, N reduction lowered ANPP by 20% relative to N addition plots. On the other hand, the reduction of insect herbivores did not alter plant richness (α diversity) yet consistently promoted Shannon's evenness, relative to plots where insect herbivores were present. Further, insect herbivores promoted spatial-temporal β diversity. Overall, we found that the relative importance of top-down and bottom-up controls of plant ANPP, plant α diversity, and composition (β diversity) can vary significantly in magnitude and direction. In addition, their effects varied through time, with bottom-up effects influencing ANPP quickly while the effects of top-down factors emerging only late in the experiment to influence plant community composition via shifts in plant dominance.
AB - Top-down effects of herbivores and bottom-up effects of nutrients shape productivity and diversity across ecosystems, yet their single and combined effects on spatial and temporal beta diversity is unknown. We established a field experiment in which the abundance of insect herbivores (top-down) and soil nitrogen (bottom-up) were manipulated over six years in an existing old-field community. We tracked plant α and β diversity - within plot richness and among plot biodiversity- and aboveground net primary productivity (ANPP) over the course of the experiment. We found that bottom-up factors affected ANPP while top-down factors influenced plant community structure. Across years, while N reduction lowered ANPP by 10%, N reduction did not alter ANPP relative to control plots. Further, N reduction lowered ANPP by 20% relative to N addition plots. On the other hand, the reduction of insect herbivores did not alter plant richness (α diversity) yet consistently promoted Shannon's evenness, relative to plots where insect herbivores were present. Further, insect herbivores promoted spatial-temporal β diversity. Overall, we found that the relative importance of top-down and bottom-up controls of plant ANPP, plant α diversity, and composition (β diversity) can vary significantly in magnitude and direction. In addition, their effects varied through time, with bottom-up effects influencing ANPP quickly while the effects of top-down factors emerging only late in the experiment to influence plant community composition via shifts in plant dominance.
U2 - 10.1111/oik.02579
DO - 10.1111/oik.02579
M3 - Journal article
AN - SCOPUS:84945568436
SN - 0030-1299
VL - 125
SP - 566
EP - 575
JO - Oikos
JF - Oikos
IS - 4
ER -