Effects of gap-model thinning intensity on the radial growth of gap-edge trees with distinct crown classes in a spruce plantation

Abstract

Key message Radial growth responses of gap-edge trees to GT intensity greatly depends on microclimate condition (soil temperature and PAR) within gaps and their abilities in competing and utilizing the limited resources. Abstract Gap-model thinning (GT) is an effective management technique to improve the productivity of dense monoculture plantation. However, how GT intensity influence inter-and intra-annual radial growth of the gapedge trees remains an open question. In order to explore this question, we implemented an experiment with four treatments (control and gap sizes of 74, 109, and 196 m 2 ) in a 30-year-old spruce (Picea asperata) plantation in 2008. We used dendrochronological method to explore dynamic of the basal area increment (BAI) of gap-edge trees (n = 127) from 2009 to 2012 after GT treatments. We found that effects of GT on the BAI of gap-edge trees highly depended on GT intensity and their crown classes. The large gaps significantly increased the BAI of gap-edge trees and further the latewood growth responded more sensitively than the earlywood, whereas the influences of the small and intermediate gaps were weak; the large gaps effectively improved the BAI of the dominant trees, following by the intermediate, but not for the suppressed trees. Our results also displayed that the earlywood increment was strongly related to the soil temperature in spring and the latewood formation was influenced by the photosynthetically active radiation in autumn. It was eventually concluded that dynamic radial growth of gap-edge trees were driven by the improved microclimate caused by GT and their abilities in competing and utilizing resources. The present study highlights the importance of setting appropriate GT intensity and choosing the felled trees in GT operation.

Research History of Forest Gap as Small-Scale Disturbances in Forest Ecosystems

“…Forest gaps provide space for the radial growth of border trees but simultaneously increase the asymmetry and risk of fracture of the canopy [144,145]. Lianas are strong competitors for tree regeneration and are major builders of ecological niches [146], preventing trees from regenerating in gaps, thus creating a high-light environment that favors the continued proliferation of lianas and inhibits tree regeneration and diversity [147].…”

Effect of thinning-induced gap size on soil CO2 efflux in a reforested spruce forest in the eastern Tibetan Plateau

“…The canopy leaf area index (LAI) was approximately 3.5, and the tree canopy coverage was 81% at the end of the 2008 growing season (Table 1). The major understory shrubs and herbs are Phlomis umbrosa, Asparagus filicinus, Thladiantha davidii, Plantago major, Sinosenecio oldhamianus, Carpesium divaricatum, Prenanthes henryi, Rosa sericea, Thalictrum uncinulatum (Jiang et al, 2011;Zhao et al, 2015). The soil at the experimental site was characterized as an Udic Luvisols (IUSS Working Group WRB, 2007).…”

Effects of Forest Gap on Soil Microbial Communities in an Evergreen Broad-Leaved Secondary Forest

“…For example, the felling of trees to create forest gaps is considered a sustainable practice, accelerating seedling height growth for indigenous trees or accelerating forest restoration within exotic Pinus radiata plantations [5][6][7]. Gap size is an important feature, reflecting the magnitude of disturbance and degree of environmental change [8,9]. Environmental factors, such as temperature, solar radiation, and moisture, are all strongly affected by the size of the forest gaps [6,10].…”