北京北部农牧交错区C4植物及其形态功能型和生境分析

根据野外调查和文献资料研究了北京北部农牧交错区C4植物的种类组成、形态功能型组成及其与生境的关系.该区共有野生C4植物68种,分布在7科,40个属,其中禾本科43种,莎草科16种,藜科5种.1年生（ANG和ANF）C4物种占C4植物总数的62%,它们在盐碱地、沙地、弃耕干扰地、湿地均超过这些生境C4植物分布的半数,在草地ANG和ANF超过30%;C4植物数量和C4/total在该地区的生境分布中有两个方向的变化：一是从草地到弃耕干扰地,两者均呈增加趋势,二是从草地到沙地和盐碱地呈现前者减少而后者增加的不同变化趋势,体现了农牧交错区植被退化的复杂性.

Analysis of C4 plants in term of habitats and morphological functional types in agro-pastoral ecotone North to the Beijing, China

More than 1700 C₄ plant species have been identified over the world wide since the work of Downton and Tregunna (1968). Most of these studies focused on the classification of plant species as to their photosynthetic pathway types (C₃, C₄ and CAM), geographic distribution of C₄ plants and their relationships with climatic patterns. But very few have exami the relations between C4 species and vegetation dynamics, especially in agro-pastoral ecotones. By dint of morphological functional types, C₄ plants and their relations with habitats in agro-pastoral ecotone North to the Beijing were analyzed based on field survey and references. Of the total identified 733 species in 304 genera and 66 families, only 64 species in 40 genera and7 families were found with C₄ photosynthesis. This indicated that the C₄ species mainly occurred in a few families in the region, but most of these species were common species and related with vegetation dynamics. Gramineae is the leading family with C₄ photosynthesis (43 species), Cyperaceae ranks the second (16 species), then followed by Chenopodiaceae (5 species). The significant increase of C4 species in the communities with land deterioration suggested C₄ plants remarkably response to the land-use frequency and intensity in the ecotone. The number of C₄ species and proportion of C4/total increased with desertification from RL to DC. The total number of C₄ species dropped significantly from RL to SS and SL, while proportions of C₄ species increased significantly. For each morphological functional types, C₄ proportion in ANG was much high (64%), followed by SPG (53%), HPG (18%), ANF (14%), but that in SHR and PEF were much lower (less than 1%). The proportions of ANG and ANF in DC, WE, SS and SL habitats exceeded by 50% respectively, and 30% in RL, indicating that communities were not stable in this ecotone. The findings suggest that the photosynthetic pathways, combined with morphological functional types, are efficient indications for studying the linkage between species and habitats in the region.