Stands Structure And Plant Diversity Of Pinus Tabulaeformis Plantation In The Gully Region Of Loess Plateau

Researching on stands structure and plant diversity has the important instruction function to improve forestry productivity and exert forestry function. On the base of sample investigation and canopy measurement in standard plots in the Gully Region of Loess Plateau, Pinus tabulaeformis plantation and undergrowth plant diversity were analyzed. The main conclusions are as follows:(1) There were 87 species which belonged to 25 families and 56 genera in the understory vegetations of Pinus tabulaeformis. There were 17 families, 38 genera and 70 species in herb layer, and 11 families, 17 genera and 17 species in shrub layer. The species richness was higher in herb layer than in shrub layer. The main plant under the forest of Pinus tabulaeformis were Stipa sareptana, Medicago sativa, Heteropappus altaicus, Muhlenbergia hugelii, Geranium sibiricum, Rubus parvifolius, Artemisia annua, Artemisia capillaries, Radix Sanguisorbae, Artemisia apiacea, Rubia cordifolia and Festuca parvigluma. And among them, the Niche breadth and niche overlap of Stipa sareptan, Medicago sativa, Heteropappus altaicus and Festuca parvigluma were comparatively bigger than other species.(2) The height of Pinus tabulaeformis grew slowly before 16 year-old, and then the growth rate increased gradually, after 35 year-old the height developed slowly and even stopped. The diameter at breast-height grew slowly before 16 year-old, and then increased gradually, until 40 year-old the diameter developed slowly again. So, the diameter and height of Pinus tabulaeformis grew synchronously.(3) In shady slope, the diameter distribution of half-mature forest in the density of 1800 trees·ha was comparatively reasonable; but in sunny slope, the density of 1500 trees·ha was comparatively reasonable. In shady slope, the height distribution of half-mature forest in the density of 2150 trees·ha was comparatively reasonable; but in sunny slope, the density of 1800 trees·ha was comparatively reasonable.(4) The relationship between the diameter and the stand density of the young forest was positive correlation. Half-mature forest and mature forest were respectively negative correlation. The height and the stand density of the young forest was negative correlation. The height and the stand density of half-mature forest and mature forest were positive correlation.(5) The leaf area index raised and the transmittance reduced along with the stand density increasing. In close age and density stand, the scattering site coefficient, direct light site coefficient and comprehensive light site coefficient in shady slope was bigger than those in sunny slope.(6) In the condition of shady, upper and lower degree slope, species richness index was high, and that condition promoted the understory vegetations growth. The plant distribution was well-proportioned in shady slope and lower degree slope. Species richness index of Shrub layer was less than herb layer. Species number and evenness index of half-mature forest was higher than young and mature forest. So the environment of half-mature forest was benefit for understory plant growth.