Response of understory vegetation over 10 years after thinning in an old-growth cedar and cypress plantation overgrazed by sika deer in eastern Japan

Abstract

Response of understory vegetation over 10 years after thinning in an old-growth cedar and cypress plantation overgrazed by sika deer in eastern Japan Atsushi Tamura * and Masanobu Yamane Abstract Background: Forest management strategies such as thinning have long been used to enhance ecosystem functions, especially in plantations. Thinning in plantations with high deer density, however, may not yield a desired increase in understory vegetation because deer graze on germinating plants after thinning. Here, we examine the changes in understory vegetation after thinning in plantations that have been overgrazed by sika deer to provide insight into the effects of thinning on ecosystem functions such as soil conservation and biological diversity. Methods: We conducted our survey in the Tanzawa Mountains of eastern Japan. We surveyed the change in understory vegetation within and outside of three deer exclosures on a single slope with three levels of understory vegetation cover: sparse (1%, exclosure "US"), moderate (30%, exclosure "MM"), and dense (80%, exclosure "LD") over 10 years after a 30% thinning of an old-growth cedar and cypress plantation which was overgrazed by sika deer. Results: Understory vegetation cover, biomass and species richness increased within and outside the "US" and "MM" exclosures after thinning, and biomass was greater within than outside the exclosures at 10 years after thinning. Unpalatable species dominated both "US" and "MM" exclosures before thinning, and trees and shrubs dominated within the exclosures over time after thinning. In contrast, unpalatable, grazing-tolerant, perennial, and annual species increased outside the "US" and "MM" exclosures. No noticeable changes were observed within and outside the "LD" exclosure when compared with the "US" and "MM" exclosures. Conclusions: Our results suggest that thinning a stand by 30% based on volume resulted in an increase in understory vegetation cover mainly composed of both unpalatable and grazing-tolerant species in a plantation forest where understory vegetation is sparse or moderate and sika deer density is high. We emphasize that establishing deer exclosures or controlling deer is essential to maintaining similar understory vegetation both within and outside exclosures.

Short-term effects of thinning on the development and communities of understory vegetation of Chinese fir plantations in Southeastern China

“…It has been found that the implementation of thinning practices improved the growth spaces and light transmittance in stands by reducing the canopy densities, and ultimately enhanced the growth of both the reserved trees and understory plants (Ares, Neill & Puettmann, 2010;Cheng, Yu & Wu, 2013;Verschuyl et al, 2011). Previous studies have extensively surveyed the impacts of thinning on the diversity and biomass of understory vegetation (Cheng et al, 2014;Dang et al, 2018;Tamura & Yamane, 2017;Wen, Cheng & Liu, 2008), as well as the effects on tree growth rates (Gong, Niu & Mu, 2015;Wu et al, 2015), physical and chemical characteristics of the soil (Wang et al, 2013;Zhou et al, 2016), and even the soil microbial biomass (Kim et al, 2018;Thibodeau et al, 2000), nutrient transformations (Boerner et al, 2008), and soil respiration characteristics (Akburak & Makineci, 2015;Tang et al, 2005).…”

Understory vegetation diversity, soil properties and microbial community response to different thinning intensities in Cryptomeria japonica var. sinensis plantations

“…Frontiers in Microbiology frontiersin.org were notably higher than those in the control. The main reason is that thinning results in more or larger canopy gaps and improves understory light conditions, which increases plant diversity (Tamura and Yamane, 2017). However, the effect of thinning on the richness of the herb layer was not as obvious as those in previous reports (Son et al, 2004;Muscolo et al, 2021), and the species richness was greater in the shrub layer than in the herb layer.…”

Meta‐analysis of management effects on biodiversity in plantation and secondary forests of Japan

“…Such instances are attributed to grazing by deer (Tamura & Yamane, 2017), and so the effectiveness of thinning in Japan and other northern temperate nations that similarly are experiencing high deer densities (Côté, Rooney, Tremblay, Dussault, Waller, 2004), will likely depend on local deer densities and grazing management. Such instances are attributed to grazing by deer (Tamura & Yamane, 2017), and so the effectiveness of thinning in Japan and other northern temperate nations that similarly are experiencing high deer densities (Côté, Rooney, Tremblay, Dussault, Waller, 2004), will likely depend on local deer densities and grazing management.…”

“…Our explanatory power was low for models explaining understory abundance with thinning intensity and stand age, and previous research has shown that thinning resulted in almost no increase in understory vegetation. Such instances are attributed to grazing by deer (Tamura & Yamane, 2017), and so the effectiveness of thinning in Japan and other northern temperate nations that similarly are experiencing high deer densities (Côté, Rooney, Tremblay, Dussault, Waller, 2004), will likely depend on local deer densities and grazing management.…”