湘西石漠化区湿地松-马褂木人工混交林林分结构及土壤理化性质研究

Study on the stand structure and soil physicochemical

关键词:  石漠化, 湿地松-马褂木人工混交林, 林分组成, 林分空间结构, 土壤理化性质

Key words:  rocky desertification, artificial mixed forest of Pinus elliottii and Liriodendron chinense, stand composition, stand spatial structure, physical and chemical properties of soil

摘要:

为探究湘西石漠化区湿地松-马褂木人工混交林林分结构及土壤理化性质,该研究以湘西石漠化地区湿地松-马褂木人工针阔混交林为对象,利用植物群落学分析和野外取样检测的方法,分析林分结构和土壤理化性质,运用Winklemass 1.0计算林分空间结构参数,并用三维离散随机变量分析了优势种的空间分布格局。结果表明:(1)林分内胸径(DBH)≥2 cm的林木株数为897 plants·hm^-2,隶属于15科16属。主林层为湿地松,平均DBH为32.3 cm,重要值为44.2%; 次林层为阔叶树,中幼龄林木居多,其中樟树、马褂木为优势树种,重要值分别为17.1%和13.2%。此外,还存在较多处于劣势生态位的天然更新种。(2)林木的水平分布格局偏向于随机分布(W^-=0.503); 林分整体趋向于中庸偏劣势过渡的态势(U^-=0.505); 种间隔离程度较高(M^-=0.689),林木混交状况良好。空间结构参数的三维离散随机变量表明,湿地松87.3%为优势和亚优势,马褂木41.7%为亚优势、26.9%为中庸态势,樟树23.5%为中庸态势、56.8%为劣势和绝对劣势。(3)林分土壤pH值趋于中性; 与撂荒地相比,林分土壤的容重、持水量、孔隙度、有机碳、全钾、全氮、全磷等因子均明显改善,但整体而言,林分土壤仍然较为贫瘠,局部土壤紧实,保水能力差。综上表明,湿地松、马褂木作为先锋树种生长43年后,林分有向异龄林、强度混交林演替的趋势。但林分内中幼龄阔叶树株数占比较大,近熟林出现断层,老龄针叶树占据优势生态区位,需抽针补阔、间针育阔,择伐劣势木,促使林分向阳生性阔叶树为主、中生性和耐阴性阔叶树为次的林分结构演替。该研究结果为湘西石漠化区的植被恢复、人工林结构优化和土壤改良提供了理论依据。

Abstract:

To explore the forest structure and soilphysicochemical properties of the artificial mixed forest of Pinus elliottii and Liriodendron chinense in the rocky desertification area of Western Hunan, taking Pinus elliottii and Liriodendron chinense artificial coniferous and broad-leaved mixed forest in the rocky desertification area of Western Hunan as the research object, this paper provides a theoretical basis for vegetation restoration, plantation structure optimization, and soil improvement in this area. The stand structure and soil physicochemical properties of existing stands were analyzed using plant community analysis and field sampling detection methods. Winklemass 1.0 was used to calculate the spatial structure parameters of the stands, and three-dimensional discrete random variables were used to analyze the spatial distribution pattern of dominant species. The results were as follows:(1)A total of trees of 897 plants·hm^-2 with diameter at breast height(DBH)≥ 2 cm in the stand, belonging to 15 families and 16 genera. The main forest layer was Pinus elliottii, with an average DBH of 32.3 cm and an important value of 44.2%; the secondary forest layer was the broad-leaved tree, with the majority of young and middle-aged trees. Cinnamomum camphora and Liriodendron chinense were the dominant species, with important values of 17.1% and 13.2%, respectively. In addition, there were many natural regeneration species at the disadvantaged ecological niche.(2)The horizontal distribution pattern of trees tended to be random(W^-=0.503); the overall trend of forest stands tended to transition towards mediocrity and disadvantage(U^-=0.505); the degree of interspecific isolation was relatively high(M^-=0.689), and the mixed forest was in good condition. Three-dimensional discrete random variables of spatial structure parameters showed that 87.3% of Pinus elliottii was dominant and sub-dominant, 41.7% of Liriodendron chinense was sub-dominant, 26.9% was moderate, 23.5% of Cinnamomum camphora was moderate, 56.8% was inferior and absolute inferior.(3)The pH value of forest soil tended to be neutral; compared with abandoned land, the bulk density, water capacity, porosity, organic carbon, total potassium, total nitrogen, and total phosphorus of the forest soil had significantly improved. However, the forest soil was still relatively barren, with local soil compaction and poor water retention ability. To sum up, after 43 years of growth of Pinus elliottii and Liriodendron chinense as pioneer species, the stand has a trend of succession to the uneven-aged forest and intensive mixed forest. However, the number of young and middle-aged broad-leaved trees in the forest is relatively large, and faults appear in the near mature forest. The elderly coniferous trees occupy the dominant ecological location. Needles need to be drawn to supplement the broad-leaved trees, interspersed to cultivate the broad-leaved trees, and selective felling the inferior trees, to promote the structural succession of the forest with mainly sunny broad-leaved trees, followed by mesophytic and shade-tolerant broad-leaved trees. The results of this study provide a theoretical basis for vegetation restoration, plantation structure optimization and soil improvement in the rocky desertification area of Western Hunan.