放牧对亚热带人工草地牧草构型及小格局的影响

对休牧后的亚热带人工草地及长期禁牧草地牧草种群的构型及小格局的研究结果表明。随着放牧强度的增加，鸭茅、红三叶株丛宽度逐渐变小．在对照及6只羊·hm^-2、7．5只羊·hm^-2、10只羊·hm^-2轮牧草地上，鸭茅基径的峰值分别介于6～8cm、2～4cm、0～2cm和0～2cm之间；红三叶则介于1～1．2cm、6～8cm、4～6cm和2～4cm之间；鸭茅丛密度分别为60、95．1、210．2和160丛·m^-1；单丛蘖数量分别为11．9、11．2、7．3、6．9蘖／丛．与禁牧草地相比，放牧草地鸭茅单丛蘖的数量明显减少，而丛密度则明显增加，白三叶节间长度因放牧强度增加而明显下降，为1．51～2．04cm，分枝角度则逐渐变大，介于46．5～77．3°，鸭茅、白三叶及红三叶在小格局水平上其格局规模均以1个样方(2cm×2cm)为主，并且随着放牧强度的提高，鸭茅、红三叶小格局规模进一步变小，白三叶构型及小格局的变化提高了牧草对环境资源的利用率。

Effects of grazing effect on architecture and small-scale pattern of grasses on artificial grassland in subtropical zone

This study was conducted on a 5-year artificial grassland in subtropical zone of South China. The main types of established artificial grassland there were Dactylis glomerata-Lolium prenne-Trifolium repens and D. glomerata-T. repens pastures. Four grazing intensities were designed, i.e., CK (no grazing), G1 (6 adult sheep x hm(-2)), G2 (7.5 adult sheep x hm(-2)) and G3 (10 adult sheep x hm(-2)), and all the grazing plots were rotationally grazed. The architecture and small-scale pattern of grasses on the grazed and ungrazed grassland were discussed. After a period of 5-year grazing, the plant basal width and sward height of D. glomerata and T. pratense decreased gradually. In treatments CK, G1, G2 and G3, the basal width of D. glomerata was 6-8, 2-4, 0-2 and 0-2 cm, and that of T. pratense was 1-1.2, 6-8, 4-6 and 2-4 cm, respectively. The tuft density of D. glomerata in treatments CK, G1, G2 and G3 was 60, 95.1, 210.2 and 160 tufts x m(-2), respectively. The tiller number per plant of D. glomerata decreased, while its tuft density increased significantly due to the increased grazing intensity. With the increase of grazing intensity, the internode length of T. repens decreased, while its branching angle increased. The average internode length in treatments CK, G1, G2 and G3 was 2.04, 1.69, 1.64 and 1.51 cm, while the branching angle was 46.5, 65, 73 and 77.3 degrees, respectively. The average leaf density of T. repens in treatments CK, G1, G2 and G3 was 2.9, 13.0, 4.7 and 1.0 x m(-2), while the relevant stolon density was 19.9, 101, 142 and 82.6 m x m(-2), respectively. Under moderate grazing intensity, both the leaf and stolon densities of T. repens increased. The main scale on small pattern of D. glomerata, T. repens and T. pratense was 2 cm x 2 cm, which was further decreased under higher grazing intensity in the treatments of D. glomerata and T. pratense. Considering the heterogeneity of environmental resources, the change of the architecture and small-scale pattern could be regarded as an adaptation of grasses under grazing disturbance.