A deteriorating state of affairs: How endogenous and exogenous factors determine plant decay rates

Abstract

Summary Woody plants store large quantities of carbon (C) and nutrients. As plants senesce and decay, these stores transfer to the soil or other organisms or are released to the atmosphere. Exogenous factors such as topographic position and microclimatic and edaphic conditions tied to locations affect decay rates; however, we know less about how exogenous relative to endogenous factors such as morphological, anatomical and chemical construction tied to plant species affect these rates, especially across different tissue types. We monitored stem, fine branch and leaf decay over 1 year in ‘rot plots’ distributed across four watersheds in ridge top and valley bottom habitats in a temperate deciduous oak‐hickory forest at Tyson Research Center, MO, USA, in the Ozark Highlands for 21 species of woody plants that vary in their constructions. We found poor coordination across tissues in construction and decay, which likely reflects how functional constraints on living tissues influence recalcitrance to decay. Additionally, for all three tissues, species membership and construction were better predictors of decay than was location. Of the construction traits, chemical composition including total fibre, lignin, cellulose, hemicellulose and concentrations of multiple microelements were the best predictors of decay, although the strength of these relationships differed among tissues. Synthesis. We have long known that rates of biogeochemical cycling are influenced by exogenous factors, such as climatic and edaphic factors. Here, we show across plant tissues that endogenous factors, including species identity and tissue construction, can have stronger controls on rates of decay within our study system than do exogenous factors. However, it is likely that the relative strengths of these different controls change through time and among tissues. We predict that anatomical and morphological controls may be more important at early stages and exogenous factors may be more important at later stages of decay.

Accurate forest projections require long‐term wood decay experiments because plant trait effects change through time

“…For every replicate, we measured initial wet mass. We then estimated initial dry mass from the dry mass to wet mass ratio (DMWMR) of additional segments that we collected from each harvested stem and dried to constant mass at 103°C (Zanne et al, ). The first cohort was deployed in 2009 and included wood from 16 species.…”

“…Ca, log(P), and Mn; Zanne et al, ). Anatomical traits were wood density, conduit lumen diameter (Zanne et al, ), and conduit length (Oberle, Ogle, Zuluaga, Sweeney, & Zanne, ). We also measured the fraction of cross‐sectional area represented by parenchyma and conduit walls based on microscopic analysis of radial sectors of fixed, stained cross sections from three branches per species following the same methodology as (Osazuwa‐Peters, Wright, & Zanne, ).…”

Tamm Review: Sequestration of carbon from coarse woody debris in forest soils

“…As discussed in the previous section, there is growing evidence that environmental conditions determine SOM stabilization mainly through accessibility of substrate for microorganisms (von Lützow et al, 2006;Dungait et al, 2012;Marschner et al, 2008;Klotzbücher et al, 2011). Zanne et al (2015) however found that effects related to species and tissue construction overruled exogenous effects on wood decomposition. Despite the lack of knowledge on specific driver effects on SOM stabilization, the current literature on main environmental and substrate-specific drivers of C respiration loss in forest soils and CWD will be reviewed in the next paragraphs.…”

“…These substrate factors may explain differences in decomposition rates among species and among tissues within an individual (Zanne et al, 2015). A full overview of all relevant species-specific properties is beyond the scope of this review, but an extensive overview of substratespecific drivers of decomposition can be found in Cornwell et al (2009).…”

Look Down to See What’s Up: A Systematic Overview of Treefall Dynamics in Forests

“…That said, the total amount of CWD in a given forest varies greatly with species composition, stand age, tree size, temperature, and humidity [29,33]. Moreover, landscape features such as slopes and valleys affect CWD spatial distribution and decomposition, with logs tending to move downhill where they are also susceptible to more rapid decay [34,45].…”