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植物种群结构不仅可以反映植物在不同时间阶段的生长情况,还可以反映植物在不同生境下的生长变化情况[1]。种群结构主要从高度结构、径级结构、冠幅结构等方面开展研究,可以反映出种群数量个体大小的配置分布情况也可以以此为依据推测植物种群未来的发展趋势[2]。研究植物的种群结构对于了解植物的生存现状以及对于资源利用和保护具有重要意义[3]。
川滇高山栎(Quercus aquifolioides)作为我国特有植物,主要分布在西藏、四川、云南、贵州等地,生长在海拔2000 m-4500 m的山坡向阳处或高山松林下,对于高海拔地区的水源涵养、水土保持、生物多样性保护以及生态系统的维护具有重要作用[4,5]。目前对川滇高山栎的研究主要集中在滇西北玉龙雪山[6]、川西折多山[7]以及西藏色季拉山[5]地区,研究内容涉及叶片的结构特征[8]、遗传多样性[6]等生理特性以及川滇高山栎基因克隆[9]、光合作用[10]、繁育技术研究[11]等方面;关于海拔梯度上的研究有不同海拔梯度上的光合特性的响应[12]、叶片营养元素的变化特征[13]、叶片的解剖结构特征[14]、生理生长特性[15]、遗传多样性分析[16]等,而对于色季拉山川滇高山栎在不同海拔梯度上种群结构特征的相关研究相对较少。本文综合分析色季拉山川滇高山栎在不同海拔梯度上的种群结构变化,增加对高海拔地区生态系统的认识以及高寒环境下高山植物对生境的适应[17]。本研究以西藏色季拉山川滇高山栎种群为研究对象,对其在不同海拔梯度上的种群结构变化规律进行探索研究,旨在为青藏高原地区的生态系统的维持和保护提供一定的数据理论支撑。
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在色季拉山海拔3400 m~3780 m之间设置一条由低海拔向高海拔延伸的50 m×700 m的样带,样带的坡度25~35º,采用相邻格子样方法将样带分成14个50 m×50 m的样方,每一个样方四周用铁丝围起。在小样方中进行调查,利用测高仪和卷尺测量记录样方中所有高度>1.5 m乔木的树高、胸径、冠幅、坐标,同时利用卷尺测量川滇高山栎幼树幼苗的高度、胸径、冠幅。海拔3400 m~3526 m之间区域为低海拔区域,海拔3526 m~3652 m之间区域为中海拔区域,海拔3652 m~3780 m之间区域为高海拔区域。
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根据川滇高山栎的生存环境、生活史特征和调查的数据,本文在参考卢杰[20,21]等和谢立红等[22]研究方法的基础上,利用空间代替时间的方法,即用立木径级结构分析川滇高山栎的种群结构。将川滇高山栎胸(地)径划分为XI级、高度划分为X级、冠幅划分为Ⅷ级,川滇高山栎的冠幅以圆的面积进行计算。具体划分指标如表1所示。统计各径级、高度级、冠幅级每一级别在每一样方内的数量,分别绘制分布结构图,分析种群结构。
级别
Level径级指标
Diameter index高度级指标
Height index冠幅级指标
Crown size indexI D<5,H<2 H<2 C<10 II D<5,H≥2 2≤H<4 10≤C<30 Ⅲ 5≤D<10 4≤H<6 30≤C<50 IV 10≤D<15 6≤H<8 50≤C<70 V 15≤D<20 8≤H<10 70≤C<90 VI 20≤D<25 10≤H<12 90≤C<110 VII 25≤D<30 12≤H<14 110≤C<130 Ⅷ 30≤D<35 14≤H<16 130≤C IX 35≤D<40 16≤H<18 X 40≤D<45 18≤H XI 45≤D 注:“D”为胸径/基径/cm,“H”为树高/m,“C”为冠幅/m2。
Note: "D" is DBH /cm, "H" is height /m, and "C" is crown size /m2.Table 1. Structural division level of Q. aquifolioides population
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采用Excel2016软件将川滇高山栎的径级、高度级、冠幅级在每一样方内的分布数量统计出来并相应地做出每一级别的分布结构图。
Response of Population Structure of Quercus aquifolioides to Altitude Gradient in Sejila Mountain
doi: 10.12172/202210010001
- Received Date: 2022-10-01
- Available Online: 2023-03-21
- Publish Date: 2023-08-30
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Key words:
- Quercus aquifolioides /
- Population structure /
- Altitude gradient
Abstract: In this paper, Quercus aquifolioides in Sejila Mountain was taken as the research object, and the population structure characteristics and its changing trend at different altitudes were analyzed. A 50 m × 700 m transect was set up in Sejila Mountain, Nyingchi City, Tibet Autonomous Region, and it was divided into fourteen 50 m × 50 m quadrats. The diameter class, height and crown structure of the population in each quadrat were studied respectively. According to the specific number of distribution plants, the variation rules and causes of different structures were studied according to the charts. The results showed that : (1) The best survival range of Q. aquifolioides was between 3400 m and 3550 m above sea level, and it was not suitable for the survival of Q. aquifolioides above 3600 m. The seedlings and saplings of Q. aquifolioides were distributed at an altitude of 3400 m-3780 m, and the number of trees above 3600 m was less. (2) There were more young seedlings of Q. aquifolioides, and fewer individuals grow to the young tree stage. The young seedlings had strong competitiveness in the growth process, while the competitiveness and viability were weak when they grow to the young tree stage. (3) With the increase of altitude, the diameter distribution range of Q. aquifolioides population gradually decreased, and the population density also decreased. (4) From 3400 m to 3780 m above sea level, the height structure of Q. aquifolioides population increased first and then decreased. (5) From 3400 m to 3500 m above sea level, the canopy structure of Q. aquifolioides population increased continuously, reaching the maximum at 3500 m, and then decreased with the elevation. Soil, water, temperature, and vegetation growth space were different at different altitude gradients, which caused different structural changes in the Q. aquifolioides population at different altitude gradients.