Nutrient cycling drives plant community trait assembly and ecosystem functioning in a tropical mountain biodiversity hotspot

Abstract

1) Community trait assembly in highly diverse tropical rainforests is still poorly understood.Based on more than a decade of field measurements in a biodiversity hotspot of southern Ecuador, we implemented plant trait variation and improved soil organic matter dynamics in a widely used dynamic vegetation model (LPJ-GUESS) to explore the main drivers of community assembly along an elevational gradient.(2) In the model (LPJ-GUESS-NTD, Nutrient-Trait Dynamics), each plant individual can possess different trait combinations, and the community trait composition emerges via ecological sorting. Further model developments include plant growth limitation by phosphorous (P) and mycorrhizal nutrient uptake.(3) The new model version reproduced the main observed community trait shift and related vegetation processes along the elevational gradient, but only if nutrient limitations to plant growth were activated. In turn, when traits were fixed, low productivity communities emerged due to reduced nutrient-use efficiency. Mycorrhizal nutrient uptake, when deactivated, reduced NPP by between 61 -72% along the gradient.(4) Our results strongly suggest that the elevational temperature gradient drives community assembly and ecosystem functioning indirectly through its effect on soil nutrient dynamics, and vegetation traits. This illustrates the importance of considering these processes to yield realistic model predictions.

Plant Trait Assembly in Species-Rich Forests at Varying Elevations in the Northwest Andes of Colombia

“…The negative correlation between magnesium in soils and leaf thickness emphasizes the importance of Mg concentration in leaves to enhance photosynthesis [72,73]. Alternatively, the negative correlation between leaf area and organic matter points to N limitation in high/cold elevations [74][75][76], which has been associated with low decomposition and soil mineralization rates [36,37,75]. Conversely, in our study area, phosphorus did not correlate significantly with any functional trait, which indicates that, in this region, P was not limiting for trait development [16].…”

“…In contrast, in the light-exposed canopy, plant species typically have a positive correlation between photosynthetic rate and resource allocation [35,36]. Another important yet often overlooked determinant of tree fitness and community assembly at a local scale are symbiotic root associations (e.g., mycorrhizae and nitrogen-fixing bacteria) [37]. These associations can enhance plant nutrient availability as well as modify plant responses to environmental constraints such as water or light limitation [38][39][40][41][42].…”

Soil phosphorus drives plant trait variations in a mature subtropical forest

“…In addition, recent global change has significantly altered soil P concentration in subtropical China, and the P limitation over subtropical forests is projected to be more severe (Yu et al, 2018). These studies underscore the urgent need to incorporate nutrient supply limitations into future ecological predictions (Dantas de Paula et al, 2021). However, it remains unclear whether soil P also drives the variations of plant functional traits from species to community level in the mature subtropical forests.…”

“…nutrient supply limitations into future ecological predictions (Dantas de Paula et al, 2021). However, it remains unclear whether soil P also drives the variations of plant functional traits from species to community level in the mature subtropical forests.…”

Biota‐mediated carbon cycling—A synthesis of biotic‐interaction controls on blue carbon

“…The development of ecosystem models is, however, a vital area of research, including conceptual advances in the representation of biotic interactions. Individual-based models become more mechanistic by including nutrient limitation and, at the same time, diversity in the traits of the simulated organisms, for instance, allowing for more realistic linkages between biotic interactions and carbon cycling (Dantas de Paula et al, 2021). Progress in the simplification of the mathematical description of species interactions has been made, too (Chalmandrier et al, 2021), and explicit inclusion of interactions other than competition, such as herbivory or facilitation, is discussed.…”