Articles containing the keyword 'vegetation dynamics'

Microcatchment water harvesting (MCWH) improved the survival and growth of planted trees on heavy soils in eastern Kenya five to six years after planting. In the best method, the cross-tied furrow microcatchment, the mean annual increment (MAI; based on the average biomass of living trees multiplied by tree density and survival) of the total and usable biomass of Prosopis juliflora (Sw.) DC. were 2,787 and 1,610 kg ha^-1 a^-1 respectively, when the initial tree density was 500 to 1,667 trees per hectare. Based on survival, the indigenous Acacia horrida Span., A. mellifera (Vahl) Benth. and A. zanzibarica (S. Moore) Taub. were the most suitable species for planting using MCWH. When both survival and the yield were considered, a local seed source of P. Juliflora was superior to all other species. The MAI in MCWH was at best distinctly higher than that in the natural vegetation (163–307 and 66–111 kg ha^-1 a^-1 for total and usable biomass respectively); this cannot satisfy the fuelwood demand of concentrated populations, such as towns or irrigation schemes.

The density of seeds of woody species in the topsoil was 40.1 seeds/m² in the Acacia-Commiphora bushland and 12.6 seeds/m² in the zone between the bushland and the Tana riverine forest. Rehabilitation of woody vegetation using the soil seed bank alone proved difficult due to the lack of seeds of desirable species.

The regeneration and dynamics of woody vegetation were also studied both in cleared and undisturbed bushland. A sub-type of Acacia-Commiphora bushland was identified as Acacia reficiens bushland, in which the dominant Commiphora species is C. campestris. Most of the woody species did not have even-aged population but cohort structures that were skewed towards young individuals. The woody vegetation and the status of soil nutrients were estimated to recover in 15–20 years on Vertic Natrargid soils after total removal of above-ground vegetation.

• Kaarakka, E-mail: vk@mm.unknown

In the forest areas of eastern China, there is a change from forest dominated by deciduous broad-leaved trees to forest dominated by evergreen broad-leaved trees as the latitude or altitude decreases. Different life forms have different survival strategies to deal with climate change, and studying the life form dynamics of the tree layers in the mixed forest in eastern China, with increasing temperature, can help us understand how the forest responds. This study was performed in a 1 ha plot in evergreen and deciduous broad-leaved mixed forest in Tianmu Mountain National Nature Reserve. Based on the data from two surveys (1996 and 2017), the changes in life form composition and biodiversity over the past 21 years were analyzed. We obtained the following results: (1) The proportion of evergreen trees increased from 55.0% in 1996 to 67.5% in 2017, and the dominance of evergreen species was enhanced. (2) The diversity of both life forms increased, and the tree species were more abundant. (3) The average annual recruitment rate of the evergreen species was 2.1% greater than their mortality rate, and the average annual recruitment rate of the deciduous species was 0.5% less than their mortality rate. (4) The competition among the trees in the small-diameter class (10 cm ≤ DBH < 20 cm) was fierce for many tree species. The proportion of the evergreen species in the small-diameter class was high. The life forms making up the mixed climax forest community has changed over the past 21 years, with the proportion and dominance of evergreen trees increasing significantly.

• Bai, State Key Laboratory of Subtropical Silviculture, Zhejiang A&F University, Hangzhou 311300, China E-mail: baicheng111@gmail.com
• You, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310011, China E-mail: sxyou@zju.edu.cn
• Ku, State Key Laboratory of Subtropical Silviculture, Zhejiang A&F University, Hangzhou 311300, China E-mail: 2732684475@qq.com
• Dai, State Key Laboratory of Subtropical Silviculture, Zhejiang A&F University, Hangzhou 311300, China E-mail: 757692949@qq.com
• Wang, State Key Laboratory of Subtropical Silviculture, Zhejiang A&F University, Hangzhou 311300, China E-mail: 237600341@qq.com
• Zhao, Management Bureau of Tianmu Mountain National Nature Reserve, Hangzhou 311311, China E-mail: 973659738@qq.com
• Yu, State Key Laboratory of Subtropical Silviculture, Zhejiang A&F University, Hangzhou 311300, China E-mail: yushq@zafu.edu.cn