Biotic and Abiotic Factors Controlling Respiration Rates of Above- and Belowground Woody Debris of Fagus crenata and Quercus crispula in Japan

Abstract

As a large, long-term pool and source of carbon and nutrients, woody litter is an important component of forest ecosystems. The objective of this study was to estimate the effect of the factors that regulate the rate of decomposition of coarse and fine woody debris (CFWD) of dominant tree species in a cool-temperate forest in Japan. Respiration rates of dead stems, branches, and coarse and fine roots of Fagus crenata and Quercus crispula felled 4 years prior obtained in situ ranged from 20.9 to 500.1 mg CO2 [kg dry wood]–1 h–1 in a one-time measurement in summer. Respiration rate had a significant negative relationship with diameter; in particular, that of a sample of Q. crispula with a diameter of >15 cm and substantial heartwood was low. It also had a significant positive relationship with moisture content. The explanatory variables diameter, [N], wood density, and moisture content were interrelated. The most parsimonious path model showed 14 significant correlations among 8 factors and respiration. Diameter and [C] had large negative direct effects on CFWD respiration rate, and moisture content and species had medium positive direct effects. [N] and temperature did not have direct or indirect effects, and position and wood density had indirect effects. The model revealed some interrelationships between controlling factors. We discussed the influence of the direct effects of explanatory variables and the influence especially of species and position. We speculate that the small R 2 value of the most parsimonious model was probably due to the omission of microbial biomass and activity. These direct and indirect effects and interrelationships between explanatory variables could be used to develop a process-based CFWD decomposition model.

Carbon and Nitrogen Accumulation and Decomposition from Coarse Woody Debris in a Naturally Regenerated Korean Red Pine (Pinus densiflora S. et Z.) Forest

“…Increased moisture content at high decay class can enhance the macrofauna or microbial activity within optimal moisture levels and may contribute to faster decomposition of litter [9], despite increases in chemically recalcitrant structure of tissues, such as lignins and polyphenols over time [25]. The CWD decomposition processes are affected by their position associated with moisture content and microbial factors, such as fungal species composition, biomass, and activity [27,53]. Therefore, further studies on decomposition rate should examine the effect of different types/positions of CWD, such as stumps and snags.…”

Use of a leaf chlorophyll content index to improve the prediction of above-ground biomass and productivity

“…It is also used to evaluate the productivity of many crops. Biomass dynamics are generally controlled by abiotic and biotic factors such as solar radiation, temperature, rainfall, soil nutrient, leaf area index (LAI), vegetative type, and human activities (Boutton, Tieszen & Imbamba, 1988; Keeler et al, 2015; Jomura et al, 2015; Van Der Sande et al, 2017). Crop AGB is affected by genetics, physiology, and environmental factors (Mavromatis et al, 2002), and it is usually regarded as an index for estimating yield and economic benefits in agricultural ecosystems.…”