Deliang Lu, Jiaojun Zhu, Yirong Sun, Lile Hu, Guangqi Zhang. (2015). Gap closure process by lateral extension growth of canopy trees and its effect on woody species regeneration in a temperate secondary forest, Northeast China. Silva Fennica vol. 49 no. 5 article id 1310. https://doi.org/10.14214/sf.1310

Keywords: canopy closure; recruitment; canopy opening; opening size; crown expansion; duration; hemispherical photograph

Highlights: Gap closure process by lateral extension growth can be described by quadratic functions; Large gaps (514–621 m²) had higher closure rates but lower closure percentages compared with middle (174–321 m²) and small gaps (68–125 m²); Gaps promoted woody species regeneration in early stage; Large and middle gaps would provide opportunities for filling regeneration, but regeneration in small gaps may eventually fail.

Abstract | Full text in HTML | Full text in PDF | Author Info

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 m²to 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

article id 575, category Research article

Sylvie Mussche, Roeland Samson, Lieven Nachtergale, An De Schrijver, Raoul Lemeur, Noël Lust. (2001). A comparison of optical and direct methods for monitoring the seasonal dynamics of leaf area index in deciduous forests. Silva Fennica vol. 35 no. 4 article id 575. https://doi.org/10.14214/sf.575

Keywords: Leaf Area Index; mixed deciduous forest; LAI-2000 plant canopy analyser; hemispherical photography; litter trap

Abstract | View details | Full text in PDF | Author Info

During the 1996 growing season the seasonal dynamics of the Leaf Area Index (LAI) were determined by 3 different methods in two forest types: a mixed oak (Quercus robur L.) – beech (Fagus sylvatica L.) stand and an ash dominated (Fraxinus excelsior L.) stand. The results obtained from the two indirect methods, i.e. hemispherical photography and LAI-2000 Plant Canopy Analyser (Li-COR), were compared with the results of the direct measurement of litter fall collected in litter trap systems. In this study the direct method is considered to be the reference, giving the most accurate LAI-values. Both the hemispherical photography and the LAI-2000 PCA introduced an underestimation of LAI when the actual canopy leaf distribution in the crown layer deviates from a random distribution of leaf area in space as is found in the mixed oak/beech stand. However, when the condition of random leaf distribution is nearly fulfilled (ash stand), the LAI-2000 PCA gave LAI-values which were close to the results obtained from the direct method. Regression curves with R2 > 0.93 could be calculated for both indirect methods.

Mussche, Laboratory of Forestry, Ghent University, Geraardsbergse Steenweg 267, B-9090 Melle, Belgium E-mail: sm@nn.be
Samson, Laboratory of Plant Ecology, Ghent University, Coupure Links 653, B-9000 Gent, Belgium E-mail: rs@nn.be
Nachtergale, Laboratory of Forestry, Ghent University, Geraardsbergse Steenweg 267, B-9090 Melle, Belgium E-mail: ln@nn.be
De Schrijver, Laboratory of Forestry, Ghent University, Geraardsbergse Steenweg 267, B-9090 Melle, Belgium E-mail: An.Deschrijver@rug.ac.be
Lemeur, Laboratory of Plant Ecology, Ghent University, Coupure Links 653, B-9000 Gent, Belgium E-mail: rl@nn.be
Lust, Laboratory of Forestry, Ghent University, Geraardsbergse Steenweg 267, B-9090 Melle, Belgium E-mail: nl@nn.be

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