Location

The station is located on the Huoditang Experimental Forest Farm of Northwest A&F University in the Qinling Mountains, with the altitude ranging from 800 m to 2500 m and the geographic coordinates within  33°18'～33°28'N in latitude and 108°21'～108°39'E in longitude. The altitude of tower for carbon flux observation is 2150 m, the geographic coordinates are 33° 27' 42" N latitude and 108° 28' 54" E longitude. The forest used for the current research is 50-years old and dominated by Picea asperata.

Climatic

The climate belongs to the north subtropical mountain climate, with annual average temperature 8～10℃, the annual precipitation 900～1200 mm and the frost-free period 170 days.

Vegetation and soil

There are various vegetation types distributing in this region along altitudinal gradient. Below 900 meters there is the baseband for vertical distribution of forests. It belongs to the north rim of subtropical vegetation. The typical vegetation is deciduous broad-leaved mixed forest zone with evergreen broad-leaved tree species including Trachycarpus fortunei, Lindera megaphylla. etc. Other subtropical species include Cunninghamia lanceolata, Pinus massoniana, etc. At the attitude of 900~1400 meters there is deciduousbroad-leaved forest zone, in which main species include Quercus variabilis, Quercus acutissima, Castanea mollissima, Castanea seguinii. The soil is brown forest soil. The major shrubs species present are Dalbergia hupeana, Cotinus coggygria, Coriaria nepalensis, Lespedeza bicolor, Rhus chinensis. Needle broad-leaved mixed forest can be divided into two sub-zones. At 1400~1700 meters there is Chinese pine and sharptooth oak forest zone. The major species are Quercus aliena var. acuteserrata, Populus davidiana, Toxicodendron vernicifluum, Tilia tuan. The shrubs species are Abelia biflora, Lespedeza bicolor, etc. At 1700~2100 meters there is armand pine and oak mixed forest zone. The soil is brown forest soil. The major species are Pinus armandi, Quercus aliena var. acuteserrata, Populus davidiana. Betula forest distributes at the attitude of 2100~2400 meters, mainly including Betula albo-sinensis, Betula albo-sinensis var. septentrionalis. Birchs regenerate well after cutting. At 2400~2600 meters there is fir forest. The soil is podzolic brown forest soil. The major species are Abies fabri and Picea asperata mixed. Above 2600 meters there are alpine scrubs, mainly including Rhododendron simsii, Sabina procumbens, Lonicera japonica.

The forest used for the current research is 50-year-old and dominated by Picea asperata. Mean stand height is 16 m. In the shrub layer, height varied from 80 cm to 520 cm and the percent cover was 28％. The major shrubs species present were Euonymus phellomanus, Lonicera hispida, Lindera glauca and Rubus loropetalus, together with herbs, e.g., Carex leucochlora, Deyeuxia sylvatica, Lysimachia christinae, Thalictrum minus, Anaphalis aureopunctata, Dioscorea nipponica, Rubia cordifolia, Sinacalia tangutica, and the fern, Dryopteris laeta. The soil is classified as mountain brown earth.

Observation system

Two eddy covariance systems consisting of a three-dimensional sonic anemometer (CSAT-3, Campbell Scientific, Inc., Logan, UT) and an open path infrared gas analyzer (LI-7500, LI-COR, Lincoln, NE); five layers of sensors for monitoring air temperature and air humidity (HMP45C); five layers of sensors for monitoring wind speed (CSAT3); one layer of sensor for monitoring wind direction; one sensor for monitoring net radiation (CNR1); one sensor for monitoring PAR; four layers of sensors for monitoring soil moisture and four sensible soil heat flux plates.

The height of the flux tower is 32 m. Two eddy covariance systems consisting of a three-dimensional sonic anemometer and an open path infrared gas analyzer were installed at 8 m and 25 m on the flux tower, respectively. Five layers of sensors for monitoring air temperature and air humidity were installed at 3m, 15 m, 20 m and 25 m on the flux tower, respectively. One layer of sensor for monitoring wind direction was installed at 30 m on the flux tower. One sensor for monitoring net radiation (CNR1) was installed at 25 m on the flux tower. One sensor for monitoring PAR was installed at 3 m on the flux tower. Four layers of sensors for monitoring soil moisture and four sensible soil heat flux plates were installed at 10 cm, 20 cm, 40 cm and 60 cm depth underground, respectively.

The data were sampled at 10 Hz by a data logger (CR-5000, Campbell Scientific, Logan, UT) which also calculated 30 min covariances using Reynolds block averaging.

Principal Investigator

Shuoxin Zhang

E-mail: sxzhang@nwsuaf.edu.cn