Title

Seasonality of leaf litter and leaf area index data for various tree species in a cool-temperate deciduous broad-leaved forest, Japan, 2005–2014

Authors

Shin Nagai^1§*, Kenlo Nishida Nasahara^2§, Shinpei Yoshitake³, Taku M. Saitoh³

Abstract

This paper reports seasonal data regarding leaf litter for 14 deciduous broad-leaved species and one evergreen coniferous species as well as leaf area index (LAI) data for the 14 deciduous broad-leaved species in a cool-temperate deciduous broad-leaved forest in Japan. The seasonal leaf biomass of various tree species is important for accurately evaluating ecosystem functions such as photosynthesis and evapotranspiration under climate change. However, there is a lack of freely available, long-term data. We collected litterfall every 1 to 4 weeks from September or October to November or December each year from 2005 to 2014 in Takayama, Japan (36° 08′ 46″N, 137° 25′ 23″E, 1420 m a.s.l.). After sorting the litter into leaves (according to species categories), stems + branches, and "other", we dried and weighed the litter groups. We also collected seasonal leaf data (number of leaves and leaf length and width) for each broad-leaved species, which we recorded every 1 to 4 weeks from April or May to October or November using multiple target shoots. To estimate the LAI in autumn for each deciduous broad-leaved species, we used a semi-empirical model of the vertical integration of leaf dry mass per unit leaf area. To estimate the LAI in spring and summer, we used the relationship between the LAI in autumn and the seasonal leaf data. Our data provide input, calibration, and validation parameters for determining LAI based on satellite remote-sensing observations or radiative transfer models and for use in ecosystem models.

Key words

• Deciduous broad-leaved forest
• ground-truth
• leaflitter
• leaf area index (LAI)
• leaf mass per area
• leaf seasonality
• Japan
• semi-empirical model
• species discrimination
• a decade data set

Introduction

Seasonality of leaf biomass is an important ecophysical parameter with which to evaluate ecosystem functions (photosynthesis and evapotranspiration) and forest structure. Leaf area index (LAI), defined as the total area of leaves (on a single side) per unit ground area, is an important spatial variable. At the plot scale, LAI is evaluated by destructive sampling ( Monsi and Saeki 2005) and non-destructive remote sensing of light conditions by digital camera or light sensors (Ryu et al. 2014). At the regional and global scales, LAI is evaluated from the empirical relationship between a satellite-observed vegetation index and leaf biomass or from a radiative transfer model using satellite-observed canopy reflectance data (Kobayashi et al. 2007; Zhu et al. 2013). LAI has been measured in situ around the world (Iio et al. 2014).

However, LAI includes many uncertainties caused by methods of observation (Richardson et al. 2011). For instance, when it is evaluated from the vertical relationship between light conditions (i.e., exponential reduction of transmittance) and leaf biomass within a forest, LAI is affected by clumping of leaves, stems, and branches ( Ryu et al. 2012). This method can evaluate the LAI of a whole canopy (strictly speaking, for a circle within a radius of 5 to 10 m at the observation point), but not of individual trees. On the other hand, leaf longevity (i.e., from leaf flush to leaf fall), which correlates well with climate, leaf traits, and photosynthesis, differs among tree species (Kikuzawa 1991; Wright et al. 2004; Onoda et al. 2011). To accurately evaluate the responsibility of photosynthesis capacity and growing period to climate change, we need seasonal in situ leaf biomass and LAI of forests and individual trees.

This paper reports seasonal data of leaf litter for 14 deciduous broad-leaved species and 1 evergreen coniferous species and LAI for 14 deciduous broad-leaved species in a cool-temperate deciduous broad-leaved forest in Japan. LAI was evaluated by integrative analysis of a semi-empirical model for the vertical integration of leaf dry mass per unit leaf area in autumn and the relationship between LAI in autumn and seasonality data of leaf number and leaf size, which were recorded every 1 to 4 weeks from April or May to October or November during 1 to 10 years from 2005 to 2014 from multiple shoots (Nasahara et al. 2008; Nagai and Nasahara 2017). These data will be useful for the validation of LAI based on satellite remote-sensing and for the input, calibration, and validation of models for the evaluation of ecosystem functions. The year-to-year variability of leaf litter and LAI among various deciduous broad-leaved species will improve ecologists' understanding of year-to-year responses of photosynthesis and plant phenology to climate change.

Metadata

1. TITLE

Seasonality of leaf litter and leaf area index data for various tree species in a cool-temperate deciduous broad-leaved forest, Japan, 2005–2014

2. IDENTIFIER

ERDP-2017-02

3. CONTRIBUTOR

A. Data Set Owner

Leaf litter:

Shin NAGAI
Department of Environmental Geochemical Cycle Research, Japan Agency for Marine-Earth Science and Technology
Address: 3173-25 Showa-machi, Kanazawa-ku, Yokohama, Kanagawa 236-0001, Japan
Tel.: +81(45)778-5594
Fax: +81(45)778-5706
E-mail: nagais@jamstec.go.jp

LAI:

Kenlo Nishida Nasahara
Faculty of Life and Environmental Sciences, University of Tsukuba
Address: 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8572, Japan
Tel./Fax: +81(29)853-4897
E-mail: 24dakenlo@gmail.com

B. Contact Person

Leaf litter:

Shin NAGAI
Department of Environmental Geochemical Cycle Research, Japan Agency for Marine-Earth Science and Technology
Address: 3173-25 Showa-machi, Kanazawa-ku, Yokohama, Kanagawa 236-0001, Japan
Tel.: +81(45)778-5594
Fax: +81(45)778-5706
E-mail: nagais@jamstec.go.jp

LAI:

Kenlo Nishida Nasahara
Faculty of Life and Environmental Sciences, University of Tsukuba
Address: 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8572, Japan
Tel./Fax: +81(29)853-4897
E-mail: 24dakenlo@gmail.com

4. PROJECTS

A. Titles

1. Environment Research and Technology Development Fund (S-1; Integrated Study for Terrestrial Carbon Management of Asia in the 21st Century Based on Scientific Advancement)
2. 21st Century COE Program (Satellite Ecology, Gifu University)
3. JSPS-NRF-NSFC A3 Foresight Program
4. Development of integrative information of the terrestrial ecosystem
5. Validation of terrestrial ecological information from GCOM-C (PI#116)
6. Development of evaluation of ecosystem functioning in deciduous forests by satellite remote sensing

B. Personal

Projects 1, 4, and 5.

Kenlo Nishida Nasahara
Faculty of Life and Environmental Sciences, University of Tsukuba
Address: 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8572, Japan
Tel./Fax: +81(29)853-4897
E-mail: 24dakenlo@gmail.com

Projects 2 and 3.

Hiroyuki Muraoka
River Basin Research Center, Gifu University
Address: 1-1 Yanagido, Gifu 501-1193, Japan
E-mail: muraoka@green.gifu-u.ac.jp

Project 6.

Shin Nagai
Department of Environmental Geochemical Cycle Research, Japan Agency for Marine-Earth Science and Technology
Address: 3173-25 Showa-machi, Kanazawa-ku, Yokohama, Kanagawa 236-0001, Japan
Tel.: +81(45)778-5594
Fax: +81(45)778-5706
E-mail: nagais@jamstec.go.jp

C. Funding

1. Ministry of the Environment of Japan
2. Japan Society for the Promotion of Science (JSPS)
3. JSPS
4. Global Change Observation Mission (GCOM) of the Japan Aerospace Exploration Agency (JAXA)
5. GCOM of JAXA
6. JSPS

5. GEOGRAPHIC COVERAGE

A. Geographic Description

Takayama, Gifu, Japan

B. Geographical Position:

36° 08′ 46″ N, 137° 25′ 23″ E (WGS84)

6. TEMPORAL COVERAGE

A. Begin

3 October 2005 (leaf litter)

4 May 2005 (LAI)

B. End

17 October 2014 (leaf litter and LAI)

7. METHODS

A. Study sites

We collected litterfall and LAI data in a 60-year-old cool-temperate deciduous secondary forest in Takayama, central Japan (36° 08′ 46″ N, 137° 25′ 23″ E, 1420 m a.s.l.). The site is part of the AsiaFlux network (http://asiaflux.net), the Japan Long-Term Ecological Research network (http://www.jalter.org), and the Phenological Eyes Network (http:// www.pheno-eye.org). The dominant canopy species are Betula ermanii Cham., Betula platyphylla Sukachev var. japonica Hara, and Quercus crispula Blume. Within a 1-ha permanent plot (Fig. 1), 40 deciduous broad-leaved species and 3 evergreen coniferous species grow (Ohtsuka et al. 2005). The evergreen dwarf bamboo Sasa senanensis Rehder, which reaches 1 to 2 m tall, fully covers the forest floor. The height of the forest canopy is 13 to 18 m. An 18-m-tall canopy access tower was located just outside the southeastern corner of the plot. This study site is described in detail in Ohtsuka et al. (2005), Nagai et al. (2014), and Saitoh et al. (2015).

B. Measurement methods

B-1. Leaf litter

We installed 14 litter traps within the 1-ha permanent plot in 1999. Each trap had a square aperture of 1 m × 1 m at 1 m height. We selected the locations of traps to cover typical topographic conditions (i.e., ridge, side slope, and valley) within the plot, and installed 2 extra traps around the canopy access tower in 2008 (Fig. 1). We collected litterfall (leaves, branches, fruit, and seeds) every 1 to 4 weeks from September or October (from June in one year) to November or December (Table 1). We sorted the litter into the leaves of 16 species categories (Table 2), stems + branches, and "other" (fruit and seeds), and then stored it in paper bags. After drying in an oven at 70℃ for >48 to 72 h, we weighed the bags of litter on electronic scales. We then subtracted the mean weight of 10 dried bags. This litterfall is described in Nasahara et al. (2008) and in Nagai et al. (2014, 2015).

Figure 1. Locations of litter traps

*We grouped B. ermanii, B. platyphylla, and B. maximowicziana into a single Betula group because it was difficult to distinguish among them.

B-2. Leaf area index

We estimated LAI in autumn based on the litterfall data in 14 litter traps (i.e., excluded L20 and L21) and leaf dry mass per unit leaf area (LMA). We estimated LMA of each species from leaf samples (2 to 13 leaves from the top and 2 to 8 leaves from the bottom) taken from August to October in 2006 and 2007 (Table 3; Nasahara et al. 2008).

We estimated LAI in spring and summer from the relationship between LAI in autumn and the relative seasonality of leaf area (as a proportion of the annual maximum value at each point in time) for each deciduous broad-leaved species. To obtain seasonality, we counted the leaves and measured their width and length on multiple target shoots every 1 to 4 weeks from April or May to October or November during 1 to 10 years (Table 4; Nasahara et al. 2008; Nagai and Nasahara 2017). We sampled 4 dominant (B. ermanii, Q. crispula, M. obovata, P. maximowiczii) and 2 codominant species (A. rufinerve, E. sciadophylloides) from the canopy access tower, and 3 dominant (A. alnifolia, F. crenata, T. japonica), 1 codominant (A. distylum), and 2 understory species (H. paniculata, V. furcatum) from the forest floor (Table 5). On each target shoot (1 to 3 shoots per tree), we counted the leaves and measured the length and width of 10 to 20 leaves from the top of the shoot to a colored tape tied to the shoot. To evaluate individual differences, we assessed 2 to 4 individuals of 3 dominant (B. ermanii, Q. crispula, A. alnifolia), 1 codominant (A. distylum), and 2 understory species (H. paniculata, V. furcatum). To evaluate differences between sunlit and shaded leaves of B. ermanii and Q. crispula, we assessed 1 to 4 shoots in the sunlit (top) canopy and in the shaded lower (bottom) canopy (Table 5). All the seasonality data is published in Nagai and Nasahara (2017).

To evaluate the relative seasonality of leaf area of each deciduous broad-leaved species, first we multiplied the number of leaves by the average leaf area (approximated as an ellipse; n = 10–20) of each target shoot on each observation date in each year. When we could not count the leaves and measure their width and length on target shoot in the same date, we adjusted the date. Second we calculated the relative seasonality (whereby the annual maximum of "number of leaves × average of leaf area" = 1) of each target shoot in each year. Finally we averaged the relative seasonality of target shoots for each deciduous broad-leaved species. For the Betula group and Q. crispula, we averaged the relative seasonality of target shoots in the sunlit (top) canopy and in the shaded lower (bottom) canopy. In the absence of data (e.g., "Aa" in 2005–2006 and 2009–2014), we used the average value of dominant and codominant species as surrogates (e.g., in 2005, the average of "Be", "Qc", "Fc", "Ad", and "Ar").

To estimate LAI in spring and summer, we multiplied the average relative seasonality of leaf area (0–1, linearly interpolated at a daily time step) by LAI in autumn for each deciduous broad-leaved species. For the Betula group and Q. crispula, we evaluated LAI in sunlit and shaded leaves, and present the total LAI calculated from sunlit and shaded leaves.

LAI is described in Nasahara et al. (2008), in Nagai et al. (2011, 2014), and in Potithep et al. (2013).

Note: LMA was average of top and bottom leaves.

Note: These observation dates are described in Nagai and Nasahara (2017).

Note: We grouped P. maximowiczii into "other" broad-leaved trees. These sample shoots for leaf-seasonality observation are described in detailed in Nagai and Nasahara (2017).

8. DATA STRUCTURE

A. Format type

The data files are formatted in comma-separated values (csv) format.

B. Naming rules of the data files

B-1. Leaf litter

The data files are named "2005_2014_TKY_litter_Sp_corrected.csv", where Sp is the two-letter abbreviation of the species:

• Aa: A. alnifolia
• Ad: A. distylum
• Ar: A. rufinerve
• Be: Betula group
• Es: E. sciadophylloides
• Fc: F. crenata
• Hp: H. paniculata
• Ks: K. septemlobus
• Mo: M. obovata
• Qc: Q. crispula
• Tj: T. japonica
• Vf: V. furcatum
• co: evergreen coniferous species
• oa: other Acer species
• ob: other deciduous species

B-2. LAI

The data files are named "2005_2014_TKY_LAI_Sp.csv", where Sp is the two-letter abbreviation of the species. "co" is not included for the LAI.

C. Header information

C-1. Leaf litter

Line 1 describes the dataset (labeled # at the start of line).

C-2. LAI

Line 1 describes the dataset (labeled # at the start of line).

D. Data sequence

D-1. Leaf litter

In data file "2005_2014_TKY_litter_Sp_corrected.csv", the columns include the following data:

Note: Sp is the two-letter abbreviation of the species. "corrected" (in filename) means that our open data is a higher-level data product. "Hp" in 2005 and 2006 includes litterfall in other deciduous broad-leaved species because we misclassified. NA means "not available". In this data paper, we don't open the litterfall data in evergreen dwarf bamboo S. senanensis because the litterfall was very little.

D-2. Leaf area index

In data file "2005_2014_TKY_LAI_Sp.csv", the columns include the following data:

Note: Sp is the two-letter abbreviation of the species. No LAI data in "Ks" in 2011 because of no litterfall. "Hp" in 2005 and 2006 includes LAI in other deciduous broad-leaved species because we misclassified litterfall in "Hp".

9. ACCESSIBILITY

License

This dataset is provided under a Creative Commons Attribution 4.0 International license (CC-BY 4.0) (https://creativecommons.org/licenses/by/4.0/).

10. ACKNOWLEDGMENTS

We are grateful to K. Kurumado, Y. Miyamoto, and H. Muraoka (River Basin Research Center, Gifu University), H. Mikami (University of Tsukuba), T. Motohka (Japan Aerospace Exploration Agency), T. Inoue (Japan Agency for Marine-Earth Science and Technology), and all Takayama community members for their assistance in the field. We are grateful for the editor and the two anonymous reviewers for their constructive comments and suggestions. This study was supported by a KAKENHI Grant-in-Aid for Scientific Research (B) from the Japan Society for the Promotion of Science (#15H04512).

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