ECOLOGICAL CHARACTERISTICS OF A SABINA SALTUARIA POPULATION AT TIMBERLINE ON THE SOUTH-FACING SLOPE OF BAIMA SNOW MOUNTAIN, SOUTHWEST CHINA

doi:10.17521/cjpe.2007.0108

Abstract

Abstract:

Aims Alpine timberlines are ecotones highly sensitive to disturbances and environmental changes that have become a major focus of global climate change research. Sabina saltuaria is an endemic timberline tree in the Qinghai-Tibetan Plateau. It occurs mainly on south-facing slopes and may be useful in ecological restoration of the high-altitude ecosystem. Understanding its ecological characteristics is necessary for understanding its adaptation strategies, as well as the causes and dynamics of timberline patterns in the region.

Methods We established one 0.42 hm² sample plot at timberline >4 390 m on the south-facing slope of Baima Snow Mountain, Northwest Yunnan Province. We recorded height, DBH (diameter at breast height) or diameter at base for seedlings and saplings, and location of each individual. We used a compass and electronic distance-measuring tool to record the location of each individual. We analyzed the size and DBH structure, time-specific life table, survivorship rate, mortality and hazard rate, spatial point pattern of individuals in each age-class and the co-relationships between different age classes.

Important findings Few seedlings occur at timberline in the area of our field survey (about 17 ind·hm^-2, only 1/6 and 1/14 of that of saplings and trees, respectively). Densities declined from trees to saplings to seedlings, and the number of individuals decreased gradually with greater DBH. The survivorship curve was between Deevy type Ⅱ and Ⅲ. The mortality rate curve was similar to the hazard rate curve; both exhibited a peak of mortality at 6-9 cm DBH). Spatial point pattern analysis indicated that most individuals of different age classes had a clumped distribution at different scales (the older the trees, the more aggregative the distribution pattern); however, seedlings had a random distribution at the scale of <14 m. Also the relationships among individuals in different age classes were all significantly correlated with each other. The associations were more significant between seedlings and trees.

Key words: population structure, time-specific life table, survival analysis, spatial point pattern, alpine timberline

ZHANG Qiao-Ying, ZHANG Yun-Chun, LUO Peng, WANG Qian, WU Ning. ECOLOGICAL CHARACTERISTICS OF A SABINA SALTUARIA POPULATION AT TIMBERLINE ON THE SOUTH-FACING SLOPE OF BAIMA SNOW MOUNTAIN, SOUTHWEST CHINA[J]. Chin J Plant Ecol, 2007, 31(5): 857-864.

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URL: https://www.plant-ecology.com/EN/10.17521/cjpe.2007.0108

https://www.plant-ecology.com/EN/Y2007/V31/I5/857

Figures/Tables 8

Table 1 The habitat characteristics of Sabina saltuaria at timberline of south-facing slope in the Baima Snow Mountain

海拔 Altitude (m)	样地大小 Plot size (m²)		郁闭度 Canopy coverage			坡向 Aspect		坡度 Slope			土壤类型 Soil type		土壤pH值 Soil pH			土壤有机质 Organic mass in soil (g·kg^-1)
4 394	4 200		0.2			235		28			山地棕壤 Mountain brown soil		4.97~6.24			74.2~86.3

Fig.1 Histogram of DBH classes of Sabina saltuaria population at timberline of south-facing slope in Baima Snow Mountain, Yunnan Province

Table 2 The time-specific life table of Sabina saltuaria at timberline of south-facing slope in Baima Snow Mountain

龄级 Age class	径级 DBH class (cm)	x	Δ_x	a_x	l_x	d_x	q_x	L_x	T_x	e_x	S_x	K_x
Ⅰ	0~3	1.5	3	48	1 000.00	229.17	0.23	885.42	2 500.00	2.50	0.77	0.26
Ⅱ	3~6	4.5	3	37	770.83	187.50	0.24	677.08	1 614.58	2.09	0.76	0.28
Ⅲ	6~9	7.5	3	28	583.33	270.83	0.46	447.92	937.50	1.61	0.54	0.62
Ⅳ	9~12	10.5	3	15	312.50	104.17	0.33	260.42	489.58	1.57	0.67	0.41
Ⅴ	12~15	13.5	3	10	208.33	104.17	0.50	156.25	229.17	1.10	0.50	0.69
Ⅵ	15~18	16.5	3	5	104.17	83.33	0.80	62.50	72.92	0.70	0.20	1.61
Ⅶ	18~21	19.5	3	1	20.83	20.83	1.00	10.42	10.42	0.50	0.00	1.00

Fig.2 Survival curve of Sabina saltuaria population at timberline of south-facing slope in the Baima Snow Mountain, Yunnan Province

Fig.3 Mortality rate (qx) and hazard rate (Kx) of Sabina saltuaria population at timberline in the Baima Snow Mountain, Yunnan Province

Fig.4 Point pattern of individuals for different age classes of Sabina saltuaria

Fig.5 Point pattern analysis for three age classes of Sabina saltuaria at timberline of Baima Snow Mountain

Fig.6 Point pattern analysis of paired age-class associations of Sabina saltuaria at timberline of Baima Snow Mountain

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