古尔班通古特沙漠南缘不同林龄人工梭梭林主林层和更新层特征

对古尔班通古特沙漠南缘6个不同林龄人工梭梭种群的结构特征、天然更新及影响因子进行研究.结果表明: 7年生人工梭梭林能天然更新,17年生时幼苗(高度H＜30 cm)、幼树(30≤H＜50 cm)和小树(H≥50 cm)的密度均达到“优”级,小树的平均高度和基径为1.10 m和1.91 cm.20年生人工梭梭林内母树长势最好,35%的个体树高在2.50～3.00 m,23.1%个体的基径达8.00～10.00 cm; 33年生人工梭梭林内母树高和径生长明显衰退,但自然落种更新能力依然较强; 梭梭自然落种更新密度与0～100 cm土层土壤有效氮含量的关联度最大(0.87),其次是土壤速效磷(0.84)及土壤水分含量(0.79),pH 8.1～8.6的土壤未限制更新层的营养生长.在主林层,与整个更新层个体密度关联性最高的是人工梭梭林母树生物量(0.77),而与更新层小树密度关联性最高的是种植密度(0.71)和母树年龄(0.70).

Characteristics of main layer and regeneration layer of Haloxylon ammodendron plantations at different ages on the southern edge of the Gurbantunggut Desert,Northwest China

The population structure characteristics, natural regeneration, and the influential factors of Haloxylon ammodendron plantations at six different stand ages on the southern edge of the Gurbantunggut Desert were studied. The results showed that H. ammodendron plantation at the stand age of 7 could naturally regenerate. At the stand age of 17, the densities of the seedlings (＜30 cm height), saplings (30≤H＜50 height), and small trees (≥50 cm height) reached optimal class, and the mean height and base diameter of the small tress reached 1.10 m and 1.91 cm, respectively. The parent trees in H. ammodendron plantation at the stand age of 20 grew best. The height of 35% individuals grew up to 2.50-3.00 m, and the basal stem diameter of 23.1% individuals grew up to 8.00-10.00 cm. The height and diameter growth of the parent trees in H. ammodendron plantation at the stand age of 33 apparently declined, but the regeneration ability by natural seed dispersal was still strong. The regeneration density of natural seed dispersal showed the greatest correlation with the available nitrogen content in 0-100 cm soil layer (0.87), followed by the soil rapidly available phosphorus content (0.84) and the soil water content (0.79). The soils with pH 8.1-8.6 did not limit the nutrient growth of the regeneration layer. In the main stand layer, the individual density of whole regeneration layer showed the greatest correlation with the biomass of the parent trees (0.77), while the density of regeneration layer of the small trees showed the greatest correlation with the planting density (0.71) and the age of the parent trees (0.70).