Self-thinning in four pine species: an evaluation of potential climate impacts

Abstract

Key message Self-thinning lines are species- and climate-specific, and they should be used when assessing the capacity of different forest stands to increase biomass/carbon storage. Context The capacity of forests to store carbon can help to mitigate the effects of atmospheric CO2 rise and climate change. The self-thinning relationship (average size measure ∼ stand density) has been used to identify the potential capacity of biomass storage at a given density and to evaluate the effect of stand management on stored carbon. Here, a study that shows how the self-thinning line varies with species and climate is presented. Aims Our main objective is thus testing whether species identity and climate affect the self-thinning line and therefore the potential amount of carbon stored in living biomass. Methods The Ecological and Forest Inventory of Catalonia was used to calculate the self-thinning lines of four common coniferous species in Catalonia, NE Iberian Peninsula (Pinus halepensis, Pinus nigra, Pinus sylvestris and Pinus uncinata). Quadratic mean diameter at breast height was chosen as the average size measure. The self-thinning lines were used to predict the potential diameter at a given density and study the effect of environmental variability. Results Species-specific self-thinning lines were obtained. The self-thinning exponent was consistent with the predicted values of −3/2 and −4/3 for mass-based scaling for all species except P. sylvestris. Species identity and climatic variability within species affected self-thinning line parameters. Conclusion Self-thinning lines are species-specific and are affected by climatic conditions. These relationships can be used to refine predictions of the capacity of different forest stands to increase biomass/carbon storage.

Size–Density Trajectory in Regenerated Maritime Pine Stands after Fire

“…Reported mean values of density after the fire, for maritime pine, are scarce and the ones being circulated, quite variable (due, in part, to a plot-size dependency as noticed by Freitas [7]), bringing additional inaccuracy to the expected density values at a given age. For example, three years after the occurrence of fires, Rodrigues [8] and Alegria et al [9], respectively, report densities of 42.5 seedlings of maritime pine per 25 m 2 and 960 plants per 500 m 2 (17,(0)(1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)190 plants per ha, respectively), while Calvo et al [10] refer to average values of 6.53-11.53 seedlings per m 2 (65,300-115,300 plants per hectare). Secondly, there is a gap of knowledge about the attainable maximum densities at a given size for young stands.…”

“…Research shows that shade tolerant species tend to show a lower slope [15] and a higher intercept [18], due to the variation in self-tolerance. Some of the references [19][20][21][22] indicate that the change of the trajectory and/or the maximum value of density depends on the location of the stands, as well as on the climate characteristics. Deviance from the straight line is also recurrently mentioned [23][24][25][26][27].…”

Climate-sensitive self-thinning trajectories of Chinese fir plantations in south China

“…A single self-thinning line has routinely been used to describe all conditions at a regional scale (Reyes-Hernandez et al 2013;Toïgo et al 2015). However, the boundary lines varied among sites (or regions) for a given species (Brunet-Navarro et al 2016;Charru et al 2012). In this study, we fitted self-thinning models that explain this variability at different sites to provide self-thinning trajectories accordingly.…”

“…In line with these results, we found that steeper slopes for Chinese fir occurred in wet areas (Table 3). In other regions, aridity was the primary explanation of limiting tree growth in tropical and lowland Mediterranean regions (Segura et al 2003;Banin et al 2012;Brunet-Navarro et al 2016). Water stress may alter the size symmetry of competition, as well as the level of stress (Chu et al 2010).…”

“…Pretzsch (2002) reported that substantial differences in environment may affect size-density relationships and self-thinning trends. Brunet-Navarro et al (2016) reported that self-thinning lines were species specific and affected by climatic conditions. Determining maximum stand density is crucial for both silvicultural practices and developing forest growth models.…”