Abstract
Coarse woody debris (CWD) is an essential component in defining the structure and function of forest ecosystems. Long-term dynamics of CWD characteristics not only affect the release rates of chemical elements from CWD, but also the species diversity of inhabiting plants, animals, insects, and microorganisms as well as the overall health of ecosystems. However, few quantitative studies have been done on the long-term dynamics of CWD characteristics in forest ecosystems in China. In this study, we conducted nine tree censuses between 1996 and 2016 at the Huoditang Experimental Forest in the Qinling Mountains of China. We quantified forest biomass including CWD and CWD characteristics such as decay states and diameter classes during this period and correlated with stand, site, and climatic variables. The forest biomass was dominated by live tree biomass (88%); followed by CWD mass (6%–10%). Understory biomass contributed only a small portion (1%–4%) of the overall biomass. Significant differences in average annual increment of CWD mass were found among forest stands of different species (p < 0.0001). Forest biomass, stand age, forest type, aspect, slope, stand density, annual average temperature, and precipitation were all significantly correlated with CWD mass (p < 0.05), with forest type exhibiting the strongest correlation (r2 = 0.8256). Over time, the annual mass of different CWD characteristics increased linearly from 1996–2016 across all forest types. Our study revealed that forest biomass, including CWD characteristics, varied by forest type. Stand and site characteristics (forest biomass, forest type, aspect, slope and stand density) along with temperature and precipitation played a major role in the dynamics of CWD in the studied forest ecosystems.
Highlights
Coarse woody debris (CWD) is often removed from the forest floor with the intention of avoiding forest health issues such as insect and pest infestations, and to reduce flammable material with respect to forest fires [1]
There was a significant difference in forest biomass across the three forest types and nine censuses (p = 0.0108), ranging from 122.82 ± 7.68 Mg·ha−1
The results showed that the long-term monitoring of the dynamics of forest biomass was beneficial to clarifying the role of CWD in carbon cycles of forest ecosystems
Summary
Coarse woody debris (CWD) is often removed from the forest floor with the intention of avoiding forest health issues such as insect and pest infestations, and to reduce flammable material with respect to forest fires [1]. Long-term monitoring of the dynamics of forest biomass can acquire accurate data that is vital for forest management, monitoring, and evaluation, and is crucial for the terrestrial carbon cycle. As an indispensably important constituent of forest biomass, CWD is under studied [14] and field observations are needed to support terrestrial carbon cycle modelling efforts [15]. Few quantitative studies have been done on the long-term dynamics of the CWD mass in forest ecosystems [24,25], especially on the long-term dynamics of CWD characteristics (i.e., CWD composition including log, snag and stump, decay classes, and diameter classes). The long-term dynamics of CWD characteristics affect the release rates of chemical elements from the CWD, and influence the diversity of attached vegetation, insects, and microorganisms in CWD. Important insights into CWD dynamics have been gained by linking stand assessments to CWD characteristics, which are recognized to be a reflection of the past and present stand features to some extent [26,27]
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