Using homemade stainless steel dendrometer band for long term tree growth measurements.

Dendrometer bands have been proposed as an accurate method for measuring tree growth. However, the constrained observation window and the material used in them hamper long-term tree growth monitoring. This study devised a dendrometer band made from stainless steel and primarily extended the extension length of the band spring to yield ample space to monitor diameter increments long-term. A total of more than 500 individual trees, including both coniferous and broadleaf trees, were examined. We compared the dendrometer band's long-term performance with diameter tape for 5- and 10-year measurements. The results showed that the measurements of the two methods were highly correlated (R > 0.89) in both measuring periods. Differences between the two measurements for individual trees were typically less than 5 mm, and the mean differences at a stand level were less than 2 mm. These consistent observations suggested that the dendrometer band measurements were reliable for long-term measurement. Using the dendrometer bands, we further demonstrated the annual tree growths of diameter at breast height (DBH) and basal area (BA) for ten years of measurements. The size-dependent relationships between DBH/BA growth and initial DBH were also presented. Owing to their simple installation, low cost, and reliable measurement, these dendrometer bands would be helpful in forestry and forest ecology research.

The impact of permafrost on carbon dioxide and methane fluxes in Siberia: A meta-analysis.

There are serious concerns associated with greenhouse gases (GHG) fluxes in high latitude ecosystems and how the permafrost thawing may potentially affect the global climate, through the alteration of carbon (C) dioxide (CO2) and methane (CH4) emissions. We performed a meta-analysis of 3002 observations from 104 published studies on CO2 and CH4 fluxes in Siberia (Russian Federation). Siberia is a vast region characterized by a large C-rich permafrost region, which is already degrading due to escalating climate change, and also large wetland areas, also regarded as a source of CH4. GHG fluxes were strongly controlled by location (Western, Central, Eastern, and Far East Siberia), permafrost presence and season. Maximum CO2 fluxes, in the permafrost zone, were observed in Central and Eastern Siberia. In the non-permafrost zone, maximum CO2 fluxes were found in Western Siberia. According to our analyses, CH4 fluxes in the permafrost zone were significantly different in all parts of Siberia. Thus, permafrost has a more profound effect on CH4 than on CO2 flux. The rank order of increase of CH4 emissions among the various Siberian regions is as follows: Central < Eastern < Western < Far East. In the non-permafrost area, CH4 fluxes in Western Siberia are higher than those in the Central part. Soil temperature was the only significant predictor of soil CO2 flux in the permafrost area. CH4 fluxes were well correlated with temperature and soil water content in the permafrost zone, but only dependent on temperature in the non-permafrost area. In this meta-analysis, we established several statistically significant temporal trends of long-term changes of GHG fluxes over three decades (1984-2017): an increasing trend of soil CO2 fluxes in the non-permafrost area of Western Siberia and a declining trend in the non-permafrost area of Central Siberia. There was also a significant increasing trend of CH4 fluxes in the permafrost area of Eastern Siberia, and its decreasing trend in the non-permafrost area of Western Siberia.

Correction to: Soil respiration patterns and rates at three Taiwanese forest plantations: dependence on elevation, temperature, precipitation, and litterfall.

Unfortunately, the original article (Huang et al. 2017) contained some errors. The Fig. 4 displayed incorrectly. The correct figure can be found below.

Soil respiration patterns and rates at three Taiwanese forest plantations: dependence on elevation, temperature, precipitation, and litterfall.

BACKGROUND: Soil respiration contributes to a large quantity of carbon emissions in the forest ecosystem. In this study, the soil respiration rates at three Taiwanese forest plantations (two lowland and one mid-elevation) were investigated. We aimed to determine how soil respiration varies between lowland and mid-elevation forest plantations and identify the relative importance of biotic and abiotic factors affecting soil respiration. RESULTS: The results showed that the temporal patterns of soil respiration rates were mainly influenced by soil temperature and soil water content, and a combined soil temperature and soil water content model explained 54-80% of the variation. However, these two factors affected soil respiration differently. Soil temperature positively contributed to soil respiration, but a bidirectional relationship between soil respiration and soil water content was revealed. Higher soil moisture content resulted in higher soil respiration rates at the lowland plantations but led to adverse effects at the mid-elevation plantation. The annual soil respiration rates were estimated as 14.3-20.0 Mg C ha-1 year-1 at the lowland plantations and 7.0-12.2 Mg C ha-1 year-1 at the mid-elevation plantation. When assembled with the findings of previous studies, the annual soil respiration rates increased with the mean annual temperature and litterfall but decreased with elevation and the mean annual precipitation. A conceptual model of the biotic and abiotic factors affecting the spatial and temporal patterns of the soil respiration rate was developed. Three determinant factors were proposed: (i) elevation, (ii) stand characteristics, and (iii) soil temperature and soil moisture. CONCLUSION: The results indicated that changes in temperature and precipitation significantly affect soil respiration. Because of the high variability of soil respiration, more studies and data syntheses are required to accurately predict soil respiration in Taiwanese forests.