Effects of habitat fragmentation on population structure and dynamics of the endangered plant Pterospermum kingtungense

doi:10.17520/biods.2020397

Abstract

Abstract:

Aims: Habitat destruction and fragmentation are the leading cause of biodiversity loss. Therefore, it is necessary to understand the effect of fragmentation on plant population dynamics. The present study compared the population structure and dynamics of the endangered plant Pterospermum kingtungense in fragmented habitats of different sizes (5-ha and 15-ha) and continuous forests. We sought to identify the key life history stages that affect the population dynamics of P. kingtungense, with the goal of the providing a scientific basis for the formulation of endangered plant protection and management strategies.

Methods: Censuses were conducted over a one-year (2018-2019) period in three 50 m × 100 m sampling plots in each of the three habitats. All P. kingtungense plants were measured for DBH (diameter at breast height, but ground diameter for seedlings and saplings), height, survival, and seedling replenishment. Based on the investigated demographic parameters, annual transition matrices were established for each habitat to predict the population dynamics, and the relative contribution of the population demographic parameters to the population growth rate was quantified by the elastic analysis method of the matrix model.

Results: Across the two years, we recorded an average of 33.5, 82 and 87.5 P. kingtungense individuals in the 5-ha fragment, 15-ha fragment and continuous forest plots, respectively. Saplings dominated in the three habitats, but seedlings and big trees (comprising subadult and adult) are scarce in the 5-ha forest fragment, while seedlings are abundant in the 15-ha forest fragment. The population growth rate of P. kingtungense was equal to (15-ha fragment) or approaching (5-ha fragment and continuous forests) one, suggesting that P. kingtungense populations were stable in different size fragments and continuous forests. This stability is mainly due to the high survival rates of the populations in each life cycle stages. The survival rates of adult and subadult stages contribute substantially to the population growth rate, and these are the key life cycle stages affecting population dynamics in this species. Thus the protection of large trees (i.e., adults and subadults) is key to maintaining populations of the endangered plant P. kingtungense.

Conclusion: Our findings reveal that the population size of P. kingtungense decreased and its population structure altered in the small fragmented habitat, but the effect on the population dynamics may not yet have shown themselves. Therefore, it is feasible and valuable to protect and restore the endangered plant populations even in small, fragmented habitats.

Key words: habitat fragmentation, population dynamics, Lefkovitch matrix models, population growth rate, elasticity analysis

Guoping Yang, Tao Wu, Yunfen Geng, Xiaoshuang Li, Jiabo Hao, Chunming Yuan. Effects of habitat fragmentation on population structure and dynamics of the endangered plant Pterospermum kingtungense[J]. Biodiv Sci, 2021, 29(4): 449-455.

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URL: https://www.biodiversity-science.net/EN/10.17520/biods.2020397

https://www.biodiversity-science.net/EN/Y2021/V29/I4/449

Figures/Tables 5

References 29

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生境类型 Habitat type	地理位置 Geographic location	海拔 Altitude (m)	土壤类型 Soil type	林冠高度 Canopy height (m)	郁闭度 Canopy density	样方数 No. of plots
5 ha生境片断 5-ha fragmented habitat	100°41′ E, 24°38′ N	1,440	黄壤 Yellow soil	20	0.85	3
15 ha生境片断 15-ha fragmented habitat	101°05′ E, 24°17′ N	1,352	红壤 Red soil	12	0.70	3
连续森林 Continuous forest	100°40′ E, 24°38′ N	1,485	黄壤 Yellow soil	20	0.92	2
连续森林 Continuous forest	100°38′ E, 24°43′ N	1,430	黄壤 Yellow soil	18	0.90	1

生境类型 Habitat type	地理位置 Geographic location	海拔 Altitude (m)	土壤类型 Soil type	林冠高度 Canopy height (m)	郁闭度 Canopy density	样方数 No. of plots
5 ha生境片断 5-ha fragmented habitat	100°41′ E, 24°38′ N	1,440	黄壤 Yellow soil	20	0.85	3
15 ha生境片断 15-ha fragmented habitat	101°05′ E, 24°17′ N	1,352	红壤 Red soil	12	0.70	3
连续森林 Continuous forest	100°40′ E, 24°38′ N	1,485	黄壤 Yellow soil	20	0.92	2
连续森林 Continuous forest	100°38′ E, 24°43′ N	1,430	黄壤 Yellow soil	18	0.90	1

生境 Habitat	矩阵 Matrix					特征向量 Eigen vector	种群增长率 λ
5 ha生境片断 5-ha fragmented habitat	0.0000	0.0000	0.0000	0.0000	0.0000	0.0000	0.9999
	0.0000	0.8750	0.0000	0.0000	0.0000	0.0000
	0.0000	0.0417	0.5000	0.0000	0.0000	0.0000
	0.0000	0.0000	0.50000	1.0000	0.0000	0.8889
	0.0000	0.0000	0.0000	0.0000	1.0000	0.1111
15 ha生境片断 15-ha fragmented habitat	0.8519	0.0000	0.0000	0.0000	0.1667	0.1618	1.0000
	0.1111	0.9667	0.0000	0.0000	0.0000	0.5386
	0.0000	0.0000	1.0000	0.0000	0.0000	0.0959
	0.0000	0.0000	0.0000	1.0000	0.0000	0.0599
	0.0000	0.0000	0.0000	0.0000	1.0000	0.1438
连续森林 Continuous forest	0.3333	0.0000	0.0000	0.0000	0.0909	0.0387	1.0172
	0.6667	0.9730	0.0000	0.0000	0.0000	0.5837
	0.0000	0.0270	0.8696	0.0000	0.0000	0.1069
	0.0000	0.0000	0.0435	0.8750	0.0000	0.0327
	0.0000	0.0000	0.0000	0.1250	1.0000	0.2381

生境 Habitat	矩阵 Matrix					特征向量 Eigen vector	种群增长率 λ
5 ha生境片断 5-ha fragmented habitat	0.0000	0.0000	0.0000	0.0000	0.0000	0.0000	0.9999
	0.0000	0.8750	0.0000	0.0000	0.0000	0.0000
	0.0000	0.0417	0.5000	0.0000	0.0000	0.0000
	0.0000	0.0000	0.50000	1.0000	0.0000	0.8889
	0.0000	0.0000	0.0000	0.0000	1.0000	0.1111
15 ha生境片断 15-ha fragmented habitat	0.8519	0.0000	0.0000	0.0000	0.1667	0.1618	1.0000
	0.1111	0.9667	0.0000	0.0000	0.0000	0.5386
	0.0000	0.0000	1.0000	0.0000	0.0000	0.0959
	0.0000	0.0000	0.0000	1.0000	0.0000	0.0599
	0.0000	0.0000	0.0000	0.0000	1.0000	0.1438
连续森林 Continuous forest	0.3333	0.0000	0.0000	0.0000	0.0909	0.0387	1.0172
	0.6667	0.9730	0.0000	0.0000	0.0000	0.5837
	0.0000	0.0270	0.8696	0.0000	0.0000	0.1069
	0.0000	0.0000	0.0435	0.8750	0.0000	0.0327
	0.0000	0.0000	0.0000	0.1250	1.0000	0.2381

生境 Habitat	生活史阶段 Life history stage	幼苗 Seedling	幼树 Sapling	小树 Small tree	亚成树 Subadult tree	成树 Adult tree
5 ha生境片断 5-ha fragmented habitat	幼苗 Seedling	0.0000	0.0000	0.0000	0.0000	0.0000
	幼树 Sapling	0.0000	0.0000	0.0000	0.0000	0.0000
	小树 Small tree	0.0000	0.0000	0.0000	0.0000	0.0000
	亚成树 Subadult tree	0.0000	0.0000	0.0000	0.8889	0.0000
	成树 Adult tree	0.0000	0.0000	0.0000	0.0000	0.1111
15 ha生境片断 15-ha fragmented habitat	幼苗 Seedling	0.0058	0.0000	0.0000	0.0000	0.0000
	幼树 Sapling	0.0008	0.0226	0.0000	0.0000	0.0000
	小树 Small tree	0.0000	0.0000	0.0329	0.0000	0.0000
	亚成树 Subadult tree	0.0000	0.0000	0.0000	0.0128	0.0000
	成树 Adult tree	0.0000	0.0000	0.0000	0.0000	0.9242
连续森林 Continuous forest	幼苗 Seedling	0.0050	0.0000	0.0000	0.0000	0.0000
	幼树 Sapling	0.0102	0.2250	0.0000	0.0000	0.0000
	小树 Small tree	0.0000	0.0102	0.0602	0.0000	0.0000
	亚成树 Subadult tree	0.0000	0.0000	0.0102	0.0629	0.0000
	成树 Adult tree	0.0000	0.0000	0.0000	0.0102	0.5958