Articles containing the keyword 'crown expansion'

The reach of different tree species’ crowns and the velocity of gap closure during the occupation of canopy gaps resulting from mortality and thinning during stand development determine species-specific competition and productivity within forest stands. However, classical dendrometric methods are rather inaccurate or even incapable of time- and cost-effectively measuring 3D tree structure, crown dynamics and space occupation non-destructively. Therefore, we applied terrestrial laser scanning (TLS) in order to measure the structural dynamics at tree and stand level from gap cutting in 2006 until 2012 in pure and mixed stands of Norway spruce (Picea abies [L.] Karst.) and European beech (Fagus sylvatica L.). In conclusion, our results suggest that Norway spruce invests newly available above-ground resources primarily into DBH as well as biomass growth and indicate a stronger resilience against loss of crown mass induced by mechanical damage. European beech showed a vastly different reaction, investing gains from additional above-ground resources primarily into faster occupation of canopy space. Whether our sample trees were located in pure or mixed groups around the gaps had no significant impact on their behavior during the years after gap cutting.

• Bayer, Address Technical University of Munich (TUM), Chair for Forest Growth and Yield Science, Hans-Carl-von-Carlowitz-Platz 2, 85354, Freising, Germany http://orcid.org/0000-0002-2084-3019 E-mail: dominik.bayer@lrz.tu-muenchen.de
• Pretzsch, Address Technical University of Munich (TUM), Chair for Forest Growth and Yield Science, Hans-Carl-von-Carlowitz-Platz 2, 85354, Freising, Germany E-mail: hans.pretzsch@lrz.tu-muenchen.de

Gap formation and its effects on regeneration have been reported as being important in forest development, but seldom studies concentrated on the gap closure process by lateral extension growth of canopy trees surrounding gaps. We monitored the closure process of 12 artificial gaps for 7 years with three size classes: small (from 68 m² to 125 m²), middle (from 174 m² to 321 m²), and large (from 514 m² to 621 m²); and investigated the regeneration twice in a temperate secondary forest, Northeast China. The closure process can be described through quadratic functions, which showed the closure rates slowed down with gap ages. Large gaps had a higher closure rate (39 m² a^–1) than middle gaps (25 m² a^–1) and small gaps (11 m² a^–1). According to the quadratic equations, the lateral growth could last 11, 13 and 16 years for small, middle and large gaps with a remaining size of 12, 69 and 223 m², respectively. As expected, regeneration exhibited the highest seedling density and volume in large gaps. There was no significant difference in regeneration density between middle gaps, small gaps and forest understory in the final investigation; but the volume of regenerated woody species increased significantly from small gaps to large gaps compared with forest understory. These results may provide references on the choice of appropriate gap sizes to promote the regeneration in temperate secondary forests.

• Lu, State Key Laboratory of Forest and Soil Ecology, Qingyuan Forest CERN, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, China;  University of Chinese Academy of Sciences, Beijing 100049, China E-mail: delianglu14@hotmail.com
• Zhu, State Key Laboratory of Forest and Soil Ecology, Qingyuan Forest CERN, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, China E-mail: jiaojunzhu@iae.ac.cn
• Sun, State Key Laboratory of Forest and Soil Ecology, Qingyuan Forest CERN, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, China E-mail: yirongsun@iae.ac.cn
• Hu,  Chinese Research Academy of Environmental Sciences, Beijing 100012, China E-mail: lilehu@gmail.com
• Zhang, State Key Laboratory of Forest and Soil Ecology, Qingyuan Forest CERN, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, China;  University of Chinese Academy of Sciences, Beijing 100049, China E-mail: zgq04713@163.com