Spatial structure of alpine trees in Mountain Baima Xueshan on the southeast Tibetan Plateau

Abstract

Most of the trees at treeline on the Tibetan Plateau are endemic to the Plateau. Yet little is known about these species. The study focused on the population structure, spatial patterns and associations of the treeline species Abies forestii var. georgei and Juniperus saltuaria at treeline and timberline in Mountain Baima Xueshan on the southeast Tibetan Plateau. These species form monodominant communities on the north-and south-facing slopes, respectively. Stem density, DBH-distribution, distribution pattern of different tree size classes, and intraspecific spatial association between different tree size classes of both species were analyzed. Spatial structure varied between A. forestii var. georgei and J. saltuaria, and for the same species, the spatial structures were also different from timberline to treeline. Stem density, mean tree height and young individuals of A. forestii var. georgei were significantly higher than those of J. saltuaria. For the same species, they were different from timberline to treeline, i.e., stem density and mean tree height of both species became lower. Size classes of both species were mainly clustered either at treeline or at timberline but at different scales, and spatial patterns of young J. saltuaria were mainly dominated by random patterns. Clumps of trees created more favorable microenvironments in harsh environments at treeline and timberline. Most tree size classes showed positive intraspecific spatial associations, but positive associations between size classes of J. saltuaria were not as significant as those of A. forestii var. georgei. The south-facing slope was usually subjected to varying intensities of pastoralism. Livestock disturbance greatly changed the microhabitat and reduced the number of young individuals. The potential of trees to regenerate was greatly inhibited, while A. forestii var. georgei showed greater regeneration potential. Spatial structures of J. saltuaria were also modified by this kind of human impact.

Spatial structure in four Norway spruce stands with different management history in the Alps and Carpathians

“…In this context, wind could have an important role (Popa 2006): initial gaps would be caused by wind and then filled in by large clusters of regeneration; the self-thinning processes with density-dependent mortality would then thin out the clusters. The reduction of aggregation with tree growth has been observed in different forests (Getzin et al 2008, Zhang et al 2009, Szewczyk and Szwagrzyk 2010. Moreover, the snag distribution in GIU presents an aggregated trend, confirming the density-mortality hypothesis (Kenkel 1988).…”

Spatial patterns of trees from different development stages in mixed temperate forest in the Hyrcanian region of Iran

“…We computed the 95% confidence interval of L r with 99 random permutations. In this study, the range of distances used to calculate the L-function ranged between 0 and 50 m. The maximum value of r = 50 m is equal to one half of the side of each 1-ha (100 m × 100 m) plot (Salas et al 2006;Zhang et al 2009). The software package used for the geostatistical analysis was GS + (Version 5.1, 2000) and all statistical analyses and simulations were conducted using the Programita for point pattern analysis (Wiegand 2006).…”

Opposite Tree-Tree Interactions Jointly Drive the Natural Fir Treeline Population on the Southeastern Tibetan Plateau

“…Previous treeline studies included two forest regions (LZ, DQ,) of the southeastern TP and three forest regions (CD, YS, AB) of the eastern TP [2,[28][29][30][31][32]. LZ has dense undisturbed Smith fir treelines that are driven by a moist mild climate [13,27], while the fir (Abies georgei) and juniper (Juniperus saltuaria) treelines in DQ were mainly driven by cold winter temperatures [42]. Similarly, the spruce (Picea likiangensis (Franch) Pritz var.…”