Environmental drivers of deadwood dynamics in woodlands and forests

Abstract

Abstract. Deadwood dynamics play a key role in many forest ecosystems. Understanding the mechanisms involved in the accumulation and depletion of deadwood can enhance our understanding of fundamental processes such as carbon sequestration and disturbance regimes, allowing better predictions of future changes related to alternative management and climate scenarios. A conceptual framework for deadwood dynamics has been generally accepted but has not been broadly tested with empirical data. We used a large (n ¼ 6191) data set containing measurements of live and standing dead trees, and downed woody material, representing numerous woodland and forest types from throughout the Interior Western USA, to assess relationships between environmental factors and basic elements of forest structure, with particular focus on the various components of deadwood (i.e., fine woody debris, litter, duff and large deadwood, both standing and downed). Environmental gradients emerged as the most influential factors determining structure and deadwood dynamics of these diverse vegetation types. We found that dead components are approximately proportional to the live component and that all of the various components of structure can be ordered as a function of climatic gradients representing temperature and moisture. The postulate that maximum accumulation of biomass is associated with intermediate values of temperature and moisture was only partially supported by our results, indicating that conceptualizations of deadwood dynamics must be considered in the context of the particular disturbance regimes (e.g., fire, insect outbreaks, wind) most commonly associated with particular woodland and forest types. These findings are relevant to a wide range of applications, from ecosystem modeling to development of resource management plans under alternative future climates.

Coarse Woody Debris Variability Due to Human Accessibility to Forest

“…Higher amounts of CWD, as snags, logs and stumps, were related to biomass [45,64,82,91]. It is worth noting that in the study area, the stand volume in the EAC was the highest, consequently differences between the accessibility classes are again associated with differences in the accumulation of CWD.…”

“…Forest management intensity affects the deadwood volume, which decreases from extensive management to intensive management [44]. Several studies showed that the volume of CWD in natural forest stands is proportional to the biomass of living trees at the site [45][46][47], although an amount of CWD varying greatly was found. In reserves characterized by beech forests in Europe, Christensen et al [48] indicated an average volume of 130 m 3 ha −1 , a value varying greatly which can exceed 700 m 3 ha −1 in reserves with a long history of protection.…”

The climate sensitivity of carbon, timber, and species richness covaries with forest age in boreal–temperate North America

“…This increase was driven by both above‐ and belowground carbon pools. As forests develop toward late‐seral stages, mortality of canopy trees increases through both density‐dependent and density‐independent processes (Franklin et al, ), leading to dead tree recruitment and deadwood accumulation (Garbarino, Marzano, Shaw, & Long, ) (Figure a). However, our data suggest that the increase in deadwood occurs concurrently with increases in ALC (Figure a), which is a much larger carbon pool than deadwood in our study system (e.g., up to an order of magnitude larger in 200 year old forests).…”

Climate and disturbance influence self‐sustaining stand dynamics of aspen (Populus tremuloides) near its range margin

“…Indeed, relatively continuous senescence or persistent pathogens can cause partial or selective mortality of older trees, leading to large dead wood accumulation in aging aspen stands (Brown and Simmerman , Garbarino et al. ). Moreover, as large trees die and create canopy gaps, stands may develop multi‐cohort size structures (Fig.…”

“…If aspen communities are largely fire independent and stable, we expected to find negative exponential relationships between tree size (or age) and density at both stand and landscape scales, indicating both localized capacity for self-replacement and regional stability (e.g., Rubin et al 2006). Continuous or episodic mortality of large trees (e.g., from pathogens, drought) would be expected in stable stands, facilitating regeneration via canopy openings and contributing to structural complexity (e.g., Garbarino et al 2015). In contrast, if aspen communities are primarily fire-dependent and seral, most stands would be expected to contain relatively few cohorts, and size-and age-class distributions at landscape scales would have a negative exponential form only if fire or other stand-replacing disturbance was frequent enough to maintain a majority of the landscape in young stands (Van Wagner 1978), an unlikely scenario if past fire exclusion led to a fire deficit.…”