Line thinning enhances diversity of Coleoptera in overstocked Cryptomeria japonica plantations in central Japan

Abstract

We evaluated the effectiveness of line thinning, a new silvicultural technique, toward restoring diversity of Coleoptera in overstocked Cryptomeria japonica D. Don plantations in central Japan. We compared the abundance of some common Coleoptera families between line-thinned stands and adjacent unthinned stands in two plantations: low-elevation Sugi site (4 years since thinning) and highelevation Kuchiotani site (6 years since thinning). Many bettle families comprising various functional groups such as plant feeders, wood borers, rotten wood feeders, root feeders, fungus feeders, dung feeders, and scavengers were more abundant in the line-thinned stands than in the unthinned stands. Furthermore, some important families were missing from the unthinned stands. There were strong positive relationships between Coleopteran abundance and understory vegetation. Our results suggest that line thinning may potentially increase biodiversity in overstocked C. japonica plantations by restoring important ecological processes such as food-web interactions (pollination, predation, herbivory, decomposition, parasitism, etc.), and habitat conditions.

Short-term response of coleopteran assemblages to thinning-induced differences in dead wood volumes

“…Dead wood decomposition is fast during the early phases of succession (Esseen et al, 1992), and commercially thinned forests support low volumes of large snags and logs, which means that commercially thinned stands can only sustain early colonizers of dead wood and their predators for a limited time (Stenbacka et al, 2010). Our results are already showing a decline in beetle abundance and richness in the second year after thinning, especially in the treatment with the lowest increase in dead wood (i.e., biomass removal), suggesting that resource and habitat will eventually support fewer beetles, both in terms of abundance and richness (Maleque et al, 2007). Thus, we suggest that thinning treatments be distributed systematically in plantation landscapes, both on a spatial and temporal scale, to create resource pulses (Yang et al, 2008) for beetles and associated organisms.…”

“…Animal feeders tend to be more abundant when prey are available (Hammond et al, 2004) but also when understory vegetation development provides sustainable food and shelter (Clinton, 2003). Commercial thinning creates sun-exposed understory conditions and can increase biomass, diversity, and cover of understory plants (Thomas et al, 1999), thus increasing the abundance of plant feeders and their predators (Maleque et al, 2007). Moreover, thinning-induced changes in trees and thinning-induced changes in other biotic and abiotic conditions can also increase the performance and densities of non-beetle invertebrates that can be used as prey by beetles (Moreau et al, 2006;Moreau and Quiring, 2011;Fuentealba and Bauce, 2012).…”

“…To our knowledge, this had never been documented. The commercial thinning of plantations is a good compromise for early-successional cambium consumers, plant feeders, open habitat species, poor dispersal species, as well as shade-and moist-loving habitat species because it produces fresh dead wood (Stenbacka et al, 2010), facilitates plant regeneration in the corridors, and increases microclimate and sun exposure (Maleque et al, 2007). Corridors produced by commercial thinning also allow for a greater entry of tourist beetles (Taki et al, 2010) than unthinned plantations.…”

The amplitude of dead wood resource pulses produced by plantation thinning mediates the assembly of wood‐boring beetles

“…Thus, the development of understory vegetation in thinned areas, especially where biomass was harvested, may explain the occurrence of cerambycids in these areas, despite the low abundance of woody resource (Maleque et al. , Taki et al. ).…”

Effects of management, environment and landscape conditions on establishment of hardwood seedlings and saplings in central Japanese coniferous plantations

“…Furthermore, some of the highly abundant shrub species (C. trichotomum, S. praecox and Z. piperitum) were found only in the plantations. Many of the abundant shrub species recorded in this study are known that their sprouting ability and seedling establishment were positively affected by forest floor disturbance (Goto et al, 1996;Kobayashi and Kamitani, 2000;Utsugi et al, 2006;Abe and Matsunaga, 2007;Maleque et al, 2007;Nagashima et al, 2009). Since the plantations have generally been more severely disturbed by management practices (such as weeding, cleaning and thinning) than the secondary hardwood forests, which have not been subjected to silvicultural practices for several decades (Nagaike, 2002), they have been shown to contain more shrub species than secondary (Nagaike, 2002) and mature forests (Ramovs and Roberts, 2005).…”