Sensitivity of dryland plant allometry to climate

Abstract

Patterns of plant biomass partitioning are fundamental to estimates of primary productivity and ecosystem process rates. Allometric relationships between above‐ground plant biomass and non‐destructive measures of plant size, such as cover, volume or stem density are widely used in plant ecology. Such size‐biomass allometry is often assumed to be invariant for a given plant species, plant functional group or ecosystem type. Allometric adjustment may be an important component of the short‐ or long‐term response of plants to abiotic conditions. We used 18 years of size‐biomass data describing of 85 plant species to investigate the sensitivity of allometry to precipitation, temperature or drought across two seasons and four ecosystems in central New Mexico, USA. Size‐biomass allometry varied with climate in 65%–70% of plant species. Closely related plant species had similar sensitivities of allometry to natural spatiotemporal variation in precipitation, temperature or drought. Annuals were less sensitive than perennials, and forbs were less sensitive than grasses or shrubs. However, the differences associated with plant life history or functional group were not independent of plant evolutionary history, as supported by the application of phylogenetically independent contrasts. Our results demonstrate that many plant species adjust patterns in the partitioning of above‐ground biomass under different climates and highlight the importance of long‐term data for understanding functional differences among plant species. A free Plain Language Summary can be found within the Supporting Information of this article.

Testing allometric scaling relationships in plant roots

“…Like other plant organs, roots scale according to metabolic, chemical, and structural traits, in a manner sometimes consistent with animal scaling (Niklas 2006;Reich et al 2006;Marba et al 2007;Hamilton et al 2011;Rudgers et al 2019). Roots are metabolically active organs expected to scale according to Kleiber's law.…”

Drone-derived canopy height predicts biomass across non-forest ecosystems globally

“…1, Supplementary Table 2). Mean canopy height was an accurate predictor for individual species, especially when calibrated for specific ecophenotypic and phenological conditions 15,31,41 . Model goodness-of-fit was strong, with adjusted R 2 values ranging from 0.46 to 0.99 with a mean of 0.83 ( Supplementary Fig.…”

“…1, Table 1, Supplementary Fig. 1, Supplementary Table 2) 15,22,41,42 . Importantly, however, intensive drone surveys are relatively easy to conduct over larger spatial extents of several hectares.…”

“…Species-level model slopes were generally similar within, but different between, PFTs. The similarity of densities within PFTs indicates these relationships are generally transferrable between species within PFTs, particularly for the better sampled types such as graminoids and shrubs, although phenotypic and phenological variation will limit accuracy 31,41 . Should destructive harvests for local calibrations not be possible due to resource limitations or taxon conservation status, the height-mass models described here could be used to nondestructively estimate AGB from similar drone-derived canopy height models (Table and Supplementary Table 2).…”

“…We selected species that were regionally widespread, accessible and would inform ongoing research efforts, but excluded extensively modified vegetation such as managed hedges. Sampling was undertaken during seasonal peak canopy cover to minimise differences arising from phenophase, although plant development and allometric relationships may still vary especially in more water-limited ecosystems 41 . The data collection protocol was comprehensively described by Cunliffe and Anderson 33 .…”