PHENOLOGICAL PHOTOGRAPHS OF SIBERIAN LARCH FOREST FROM 1997 TO 2000
AT SPASSKAYA PAD, REPUBLIC OF SAKHA, RUSSIA

by
Rikie Suzuki (IGCR-Tsukuba, Frontier Research System for Global Change, Japan)
Ken Yoshikawa (Faculty of Agriculture, Okayama University, Japan)
Trofim C. Maximov (Institute for Biological Problems of Cryolithozone SD RAS, Russia)

March 2001

1. Introduction

The land surface process plays an important role in the water and energy exchanges between atmosphere and ground surface. Especially, the vegetation cover is a dominant factor, that is, its transpiration activity greatly influences the water flux from land surface to atmosphere. Also the leaf canopy changes the albedo of the surface, subsequently the radiation budget is altered by seasonal changes in vegetation cover.

Recently, the condition of the land surface is remotely monitored by satellite observations, and the information on the vegetation activity has been continuously provided. Satellite-derived snow cover map has been also constructed.  The geographical and climatological implication of Siberian vegetation has been focused by using remotely-sensed data (e.g. Suzuki et al., 2000, 2001). For such remotely-sensed measurement, the ground truth information is important for the practical analysis. For instance, the measurement of satellite NOAA does not distinguish the forest canopy and forest floor. Also, the remotely sensed value cannot tell us whether the snow cover exists on the canopy or not. To validate remotely sensed data, it is strongly desired to obtain the information at the ground level.

For the study on land surface process concerning with the energy and water exchange, another important thing is to monitor the phenological aspects of the forest. Shoot elongation and the leaf/needle senescence in autumn should be the most noticeable event in taiga forest from a phenological stand point of view. As such phenological transition of the forest is closely related to the vegetation activity, it is highly required to acquire such information.

An essential and fundamental method to record the forest/snow condition and phenological transition is to take photographs of forest and tree at different phenological stages.  In this regard, photograph observation was carried out at a station Spasskaya Pad, Republic of Sakha, Russia. As a part of GEWEX Asian Monsoon Experiment (GAME), an international project under the Global Energy and Water Cycle Experiment (GEWEX), GAME-Siberia is being implemented in the Lena river basin, focusing on energy and water cycle processes (GAME-International Science Panel, 1998). One experimental site is installed at Spasskaya Pad and multi-year operation has be being conducted

2. Site description

Spasskaya Pad, the site of phenological photographing, is located at 129 degrees 37 minutes 08 seconds East, 62 degrees 15 minutes 18 seconds North, about 50km north of Yakutsk city, Republic of Sakha, Russia. The site altitude is 210msl on the terrace of Lena river that flows south to north about 15km east apart from Spasskaya Pad. This site is situated in a larch (Larix gmelinii) forest in a continuous permafrost region, where the depth of the active layer is about 1.2m.  Small portion of birch (Betula platyphylla) trees can be seen in the forest.  Bearberry (Vaccinium vitis-idea and Arctostaphulos uva-ursi) is a dominant species on the forest floor covered by the litter of larch tree. Photographs were taken at one fixed point in this forest

3. Method of photographing

Basically 5-daily photographing at the site was carried out from August 25, 1997 up to October 15, 2000. In the winter season, the frequency was reduced, and 10-daily photographing was done. There are some missing pictures due to losing film or out-of-order of the camera. All pictures were taken around noon.

The camera (automatic camera with 35mm lens) was hold by hand and pictures were taken directing toward west of the forest. Three scenes of forest were taken: forest canopy, forest floor, and forest landscape at eye level. In addition to them, scenes of shoot elongation of larch and birch were taken from spring to autumn. APS color film (25exp, ISO 100 or 400) was used.

The photograph of this web site is labeled by [Month. date_scene] (see some photographs by clicking the month in the left frame).  The upper-case alphabet character at the tail of the label stands for the scene, C: canopy, S: eye-level forest, F: floor, L: branch of larch, and B: branch of birch.

4. Phenological aspect of the forest as revealed by the photographs

4.1. Spring

In early spring (e.g. March 25, 1998; March 26, 1999; March 26, 2000), no snow or frost was found on the forest canopy, but the forest floor was still covered by snow. The snow thawing of the forest floor took place in early to mid May (e.g. May 13, 1998). At this time, the forest floor was covered by orange-color litter (e.g. May 13, 1998). The forest canopy had no green matter at this stage.

In late May, the bud break of both larch and birch trees occured, for example in the pictures on May 31, 1998, May 26, 1999, and May 25, 2000. The landscape of the forest was slightly colored in green. The foliation quickly advanced. It appears that the foliation of larch tree is at the half point of the total elongation on June 2, 1999.

4.2. Summer

It looks that the foliation from both larch and birch trees almost completed in early June (e.g. June 10, 1998 and June 10, 2000). The canopy was colored in green, and a lot of green plant appeared on the forest floor. From end of June to July, the biome of the forest should reach its mature stage. From the photographs on June 25, 1998, July 10, 1999, and July 1, 2000, fully elongated shoots of larch can be seen. On the forest floor, there was more green plant than in May. The eye-level photograph tells us that the forest was colored in green except for the trunk of trees.

4.3. Autumn

The leaf of birch turned yellow in late summer to early autumn (e.g. between August 25 and 30, 1999), then almost all leaves quickly fell out from the branch (September 5, 1999). As for larch tree, the senescence is later than birch tree that was seen in mid September (e.g. around September 15 in all three years). The larch leaf completely turned yellow by the end of September (e.g. September 20, 1997; September 26, 1998). The leaves fell out in the end of September to beginning of October (e.g. before October 5, 1997; September 30, 1999; September 30, 2000), at the same time, snow began to cover the forest floor. The snow depth increases toward the winter season. On November 20, 1997, the forest canopy was covered by frost and snow in addition to the forest floor.

4.4. Winter

The forest canopy has a dense frost and snow cover in November to January (e.g. December 27, 1999). No green matter was visible in the forest in this season. The frost and snow on the forest canopy started to diminish from February, and it completely disappeared in the end of February to March (e.g. March 26, 2000). The forest floor was continuously covered by thick snow throughout the winter.

4.5. The timing of major phenological events in each year

Following table summarizes the time of major event of the forest as roughly revealed by the photographs. 'Foliation' is identified when green leaf can be seen on the branch. 'Senescence' means the start time to turn yellow.

5. Summary

Photographs were taken at the forest of Spasskaya Pad to monitor the phenological characteristics of the forest at 5 or 10 day interval from August 1997 to October 15, 2000. From the photographs, following phenological characteristics of the forest at Spasskaya Pad was summarized. Snow thawing from the forest floor takes place in early May, and the foliation of birch and larch trees starts in the end of May. The mature stage of the forest can be seen in June and July. The senescence time of birch starts in late August that is earlier than that of larch (mid September). Snow cover can be seen from September or October over the forest floor until April in next year. In November to January, the frost and snow cover develop on the forest canopy, but they diminish and disappear by March that is about 2 month earlier than the snow thawing from the forest floor.

The information introduced in this paper should be worthwhile as a ground truth database for the satellite remote sensing data concerning with the phenology of the Siberian forest. This paper also provide a meaningful information to analyze the phenological aspect of taiga ecosystems.

Acknowledgements

This research project was conducted under the framework of GAME-Siberia. The authors are grateful to all the colleagues who took the photographs at Spasskaya Pad. This study was partly supported by the grant-in-aid for scientific research from the Ministry of Education, Culture, Sports, Science and Technology (MEXT) in Japan ("Better Understanding of Water and Energy Circulation in a Continental Scale Based on Satellite Remote Sensing", 08241105; "Tree Leaf Phenology in Relation to Geographical Patterns in Evergreenness and Deciduousness of Forest Trees",12304047). This website was constructed being supported by Mr. Hisanori Tanaka (University of Tsukuba) and Mr. Osamu Arakawa (University of Tsukuba).

References

GAME-International Science Panel. 1998. GEWEX Asian Monsoon Experiment (GAME) Implementation Plan.
Suzuki R, Tanaka S, Yasunari T. 2000. Relationships between meridional profiles of satellite-derived vegetation index (NDVI) and climate over Siberia. International Journal of Climatology, 20, 955-967.
Suzuki R, Nomaki T, Yasunari T. 2001. Spatial distribution and its seasonality of satellite-derived vegetation index (NDVI) and climate in Siberia. International Journal of Climatology, 21(in press).