渭北黄土区人工刺槐林生长与生物量效应

Growth and biomass effects of Robinia pseudoacacia plantation in Weibei Loess Plateau

通过比较黄土区不同立地条件刺槐人工林各器官生长指标及126株解析木生物量实测资料,分析不同密度刺槐人工林的生长与生物量状况,揭示林分不同径级的密度变化特征,拟合单株生物量与胸径、树高的生长模型。结果表明:在撂荒地、坡耕地和荒坡地营造刺槐林后,随林龄的增长和密度的变化,单株总生物量均表现为平均树干占47.1%,树枝和根系分别占22.22%和25.41%,树叶和果实的比例最低,而且高密度林分内林木的树干生物量均小于低密度林分。同时,30年撂荒地造林密度为1 050株/hm2时,24 cm径级树干生物量占65.5%;35年坡耕地造林密度950株/hm2时,24 cm径级树干生物量占58.39%;30年荒坡地造林密度1 410株/hm2时,24 cm径级树干生物量占51.6%。另外,30年中小径级的树木占林分总密度的67.62%,35年中径级的树木占林分总密度的52.84%。从刺槐生长状况分析结果看,黄土区刺槐人工林的适宜密度为950～1 050株/hm2,并应对该区生长30～35年的中径级刺槐林进行合理间伐利用,方可获得较高的生物产量。

Based on comparative studying organ growth indicators of Robinia pseudoacacia plantation under different site conditions in Weibei Loess Plateau and 126 analytic trees biomass data, this paper analyzed the growth and biomass of R. pseudoacacia plantations in different densities, investigated the density variation characteristics of different diameter classes, which were used to fit the growth model of individual biomass related with diameter at breast height and tree height. The results showed that： after planted, with forest age increasing and density changes, the trunk, branches and roots accounted for 47. 1%, 22.22% and 25.41% of R. pseudoacacia biomass respectively no matter in the abandoned land, sloping land or wasteland. In addition, leaves and fruits had the lowest content and trunk biomass in high-density stands was less than that in low-density stands. Meanwhile, when planting density of 30 years abandoned land was 1 050 plants/hm2, 24 cm diameter class of stem biomass accounted for 65.5%. When planting density of 35 years slope farmland was 950 plants/hm2, 24 cm diameter class trunk biomass accounted for 58.39%. When planting density of 30 years wasteland was 1 410 plants/ hm2, 24 cm diameter class trunk biomass accounted for 51.6%. In addition, the 30-year-old trees withmid and small diameter class accounted for 67 with mid diameter class accounted for 52.84% 62% of the total stand density, and the 35-year-old trees of the total stand density. Therefore, on the basis of R. pseudoacacia plantations growth status analysis results, the most suitable plantations in Weibei Loess Plateau was 950 - 1 050 plants/hm2. Also, diameter class of 30 -35 years R. pseudoacacia plantations could achieve a area. reasonable higher biomass yie of mid in this