Photosynthetic Pathways and Life Form Types for Native Plant Species from Hulunbeier Rangelands, Inner Mongolia, North China
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PHOTOSYNTHETICA 42 (2): 219-227, 2004 Photosynthetic pathways and life form types for native plant species from Hulunbeier Rangelands, Inner Mongolia, North China R.Z. WANG Laboratory of Quantitative Vegetation Ecology, Institute of Botany, the Chinese Academy of Sciences, No. 20 Nanxincun, Xiangshan, Beijing, 100093, China Abstract Photosynthetic pathway types (C3, C4, and CAM) and life forms of native species from Hulunbeier rangelands, north China were studied. Of the total 258 species, 216 species in 132 genera and 42 families had C3 photosynthetic pathway, including dominant herbs, e.g. Stipa baicalensis Roshev. and Leymus chinensis (Trin.) Tzvel., Filifolium sibiricum Kitam. and Arudinella hirta (Thunb.) Koidz. 38 species in 28 genera and 10 families were found with C4 photosynthesis, and 4 species in 2 genera and 1 family had CAM photosynthetic pathway. The occurrence of C4 species was common in Gramineae and Chenopodiaceae, and the two families were leading ones within C4 plants. More than 52 % of the total 258 species were in H form, 21 % in Th form, 19 % in G form; the other life form types, e.g. Ch, M, N, and HH, formed less than 3 %. 68 % of C4 species were in Th form and 24 % in H form, indicating that these types were the dominant life forms for C4 species in the rangeland region. The occurrence of C4 species was closely related with plant habitats, disturbed lands had the highest C4 abundance (55 % of the total C4 species), followed by grasslands and sandy soil, and forests had the lowest C4 abundance (8 %). Hence the occurrence of C4 species could be efficient indicator for rangeland dynamics in Hulunbeier rangelands. Additional key words: C3, C4 and CAM plants; meadow and steppe. Introduction Hulunbeier region (47o20'–50o12'N, 118o31'–121o03'E) researches on this type of rangelands mainly focused on covers an area of about 84 000 km2 in the northeastern rangeland classification (Pan 1992, Zhang and Liu 1992, Inner Mongolia, China, about 85 % of which is range- Zhu 1993) and rangeland grazing (Li and Xiao 1965), but lands. This type of rangelands has been grazed by noma- the photosynthetic pathway types, life forms, and their dic herds for centuries. The high palatability of herbs roles in rangeland management decision remain unclear. with herbage production superior both in quality and Classification of photosynthetic pathway types and quantity makes the rangelands ideal for grazing and analysis of their relation to climatic patterns have been forage in north China. More recently, sedentary agricul- well documented for many vegetation types (Downton ture has resulted in heavier grazing pressure and farm cul- 1975, Teeri and Stowe 1976, Raghavendra 1978, Teeri tivation, which have led to increased soil erosion and de- et al. 1980, Takeda and Hakoyama 1985, Collins and sertification, an apparent deterioration in rangeland qua- Jones 1985, Ueno and Takeda 1992, Li 1993, Redmann lity and productivity (Zhang and Liu 1992). Within the et al. 1995, Collatz et al. 1998, Pyankov et al. 2000). past 5 years there has been a move toward greater regula- Some studies deal with the relations between photosyn- tion of rangeland management in order to reduce range- thetic pathway types and land use (Williams and Markley land deterioration and permit its sustainable utilization, as 1973, Redmann et al. 1995, Wang 2002a,d), but only a well as to improve the local environments. Such range- few look at the relationships of the photosynthetic path- land management regulation (e.g. warm season, cool sea- way types with life forms (Wang 2002b,c). Observations son, and farm cultivation) must ultimately be based on showed that photosynthetic pathway types combined with scientific principles and will require more knowledge of life forms could be efficient indicators for rangeland dy- the rangelands, e.g. rangeland vegetation types, dyna- namics. The objective of the present study was to investi- mics, and photosynthetic pathway compositions. Previous gate the photosynthetic pathway types and life forms ——— Received 19 January 2004, accepted 17 March 2004. Fax: 0086-01-82591781, e-mail: [email protected] Acknowledgments: I am grateful for the funding provided by National Key Basic Research Special Foundation Project (NKBRSF project G2000018607) and in part by the Key Projects of Knowledge Innovation of Chinese Academy of Sciences (KSCX1-08-03). 219 R.Z. WANG for the native plant species from Hulunbeier rangelands, better understanding C3 and C4 plants in the region and north China. This study may bring new information for their relations with rangeland ecosystems and land use. Materials and methods The study was conducted in Hulunbeier rangelands, a ty- 70–80 % falls between June and August (Zhang and Liu pical rangeland region distributed at the eastern end of the 1992). Eurasian steppe zone, with the main location in China Floristic species were obtained from both field survey being the eastern part of Inner Mongolia. The elevations and references published from 1980 to 2002 (Commissio- of the rangelands vary from 600 m in the west to 1 000 m ne Redactorum Flora Intramongolicae 1980, Pan 1992, in the east. Local vegetation has been classified as tempe- Chen and Jia 2002). Photosynthetic pathway types for the rate meadow and steppe, humid rangelands dominated by plant species were determined by stable carbon isotope meso-xerophytes and associated mesophytes. Common ratio (δ13C) and from the references published between dominant species in the rangelands are Stipa baicalensis 1985 and 2002 (e.g. Takeda and Hakoyama 1985, Pan Roshev. and Leymus chinensis (Trin.) Tzvel., and subdo- 1992, Li 1993, Redmann et al. 1995, Yin and Li 1997, minants Filifolium sibiricum Kitam. and Arudinella hirta Pyankov et al. 2000, Wang 2002b,c). Plants with δ13C (Thunb.) Koidz. Most of the region has mountain dark values above –19 ‰ were considered to have the C4 pho- brown chernozem and chestnut soils from the east to the tosynthetic pathway, and those with δ13C values less than west or from grassland–forest ecotone to typical steppe. –21 ‰ to have C3 photosynthesis (Redmann et al. 1995, The main characteristics of the climate of the region are Yin and Li 1997). Plants identified in the region were cold, dry, and frequently windy spring; cool and short classified into seven life form types: hemicryptophyte summer; early autumn frosts; and long cold winter with (H), geophyte (G), therophyte (Th), chamaephyte (Ch), much snowfall. Mean air temperature varies from –26 °C macrophanerophyte (M), nanophanerophyte (N), and hy- in January to 19 °C in July. Moisture gradient is very drogeophyte (HH) (Li 1979, Wang 2002b,c). Plant distri- steep, with annual precipitation varying from 450 mm in bution habitats were classified into five main types: frost the east forests to 250 mm in the west steppes, of which (FO), grassland (GL), disturbed land (DB), sandy soil (SS), and wetland (WL) (Table 1). Results Rangeland floristic composition: 258 vascular plant The occurrence of C4 species in the rangeland region species, about 20 % of the total species identified in the was common in Chenopodiaceae (47 % of the total Hulunbeier rangelands, in 155 genera and 46 families Chenopodiaceae species), e.g. Kochia prostrata (L.) were selected into those having C3, C4, and CAM photo- Schrad., K. scoparia (L.) Schrad., K. sieversiana (Pall.) synthesis (Table 1). One species (Ephedra sinica Stapf.) C.A. Mey., Salsola collina Pall., and S. pestifer A. was identified in Gymnospermae, the others in Angio- Nelson, and in Gramineae (46 % of the total grasses), e.g. spermae. Of the total 257 Angiospermae species, 182 Digitaria ciliaris (Rotz.) Koel., Eragrostis pilosa (L.) species were found in Dicotyledoneae, e.g. Compositae P.B., E. poaeoides Beauv., Eriochloa villosa (Thunb.) (46 species), Fabaceae (21 species), Chenopodiaceae Kunth L. Most of the C4 species in these two families (17 species), Rosaceae (14 species), and Ranunculaceae were annual species, some of them having great tolerance (11 species). 75 species belang to Monocotyledoneae, e.g. to arid environments. 74 % of the total C4 species identi- Gramineae (50 species), Cyperaceae (9 species), and fied in Hulunbeier rangelands belong to Gramineae Liliaceae (9 species). As for photosynthetic pathway ty- (53 % or 20 of 38) and Chenopodiaceae (21 % or 8 of pes, 216 species in 132 genera and 42 families were 38), suggesting that these two families are the leading found with C3 photosynthesis, 38 species in 28 genera families with C4 metabolism. and 10 families with C4 photosynthesis, and 4 species in 2 genera and 1 family with CAM photosynthesis (Table 1). Plant life form types and distribution patterns: There The number of C4 species was no more than 3 % of the were seven life form types for the plants from Hulunbeier total plant species identified in local flora, even though it rangelands (Fig. 1A). More than half (54 %) of the total was about 15 % of those listed in Table 1. For the 182 Di- 258 species were hemicryptophytes (H), and 6.5 % of H cotyledoneae species listed in Table 1, 90 % was C3 formed species with C4 photosynthesis. In the rangeland species, 8 % was C4 species, and 2 % was CAM species. region, therophyte (Th) was the second leading life form Of the 75 Monocotyledoneae species, however, 31 % type, about 21 % of the total species in Table 1, but half were with C4 photosynthesis, the other 69 % with C3 pho- of the Th form species were C4 plants, which was about tosynthesis. This indicated that the occurrence of C4 68 % of the total C4 species (Fig. 1B, Table 1). Of the species in Monocotyledoneae was as high as about 4 total 258 species, 10 % was the Th form C4 species, while times that in Dicotyledoneae in the region. for the H form it was only 3.5 %. Only one C4 species 220 PHOTOSYNTHETIC PATHWAYS AND LIFE FORM TYPES FOR NATIVE PLANT SPECIES Table 1.