Quantitative Characteristics Of The Loess Plateau Cai Song Community And Seedling Regeneration Research

Pinus tabulaeformis f. shekannesis, the individual groups, means a variation of P. tabulaeformis species in the Loess Plateau, which distribution is extremely limited. The communities only appear in Shaanxi-Gansu border, which is the rare precious species of native tree species gene pool. The population in this region constitutes important component of the ecosystem, improve the local environment and plays an important role. the rational management, protection, expanding P. tabulaeformis f. shekannesis forest resources is very important.However, due to the range of small communities, protection and updating are strengthen discussion and study are also need. To elucidate the regeneration dynamics of populations and seedlings, the mortality and causes of seedlings, a systematic study on populations quantitative features and size structure of P. tabulaeformis f. shekannesis and Quercus wutaishanica, as well as the regeneration characteristic of seedlings in different slopes in P. tabulaeformis f. shekannesis were accomplished by using quadrat sampling method, which provided the basis of making reasonable conservation and management measures for protecting the present natural forest effectively and expending its distribution scope.The main conclusions were as follows:(1) populations and seedlings of P. tabulaeformis f. shekannesis in pure and mixed forest, as well as Q. wutaishanica population in pure forest appeared to distribute in an inversed'J'shape, which indicated they were developing populations. Q. wutaishanica in mixed forest was a grown up population. The quantity of seedlings in low class size are larger, which shows abundant reserve resources of Q. wutaishanica population. (2) the average height of P. tabulaeformis f. shekannesis population was greater than that:In the mixed community. Crown size decreased with the individuals and the crown size structure presented reverse pyramid-like form, most individuals were 1 m2. (3) In the P. tabulaeformis f. shekannesis community, the DBH was significantly related with the height. The relation between height and DBH was more obvious than that between height and crown size, the relation between crown size and DBH was more obvious than that between crown size and height. (4) environmental conditions in the mixed forest were more suitable for the earlier seedlings but less for later growth. The density of P. tabulaeformis f. shekannesis seedlings was lower than that of Q. liaotungensis, and the seedling bank of P. tabulaeformis f. shekannesis population in this area was also poor. Comparatively, P. tabulaeformis f. shekannesis population might be more suitable for the growth of Q. wutaishanica. (5) the natural regeneration of P. tabulaeformis f. shekannesis seedlings was closely related to the slope positions. The P. tabulaeformis f. shekannesis seedlings in the up-slope and mid-slope were similar in number and density, while in the low-slope the number and density were much lower. The height of P. tabulaeformis f. shekannesis seedlings in different slopes varied little and was consistent with the average height. (6) the height of seedlings was closely related to the shrub canopy. The density of seedlings was related to the litter layer, but the density and height of seedlings were all unrelated with the tree and the herb layer. (7) In conclusion, we suggest that during the protection and recovering of the P. tabulaeformis f. shekannesis forest, different cultural measures should be taken in different slopes. In order to expand population, seedlings were cultivated artificially, which should be strengthened. We also advise to establish seed bank for providing seed provenance in the future.