Thinning affects understorey tree community assembly in monoculture plantations by facilitating stochastic immigration from the landscape. Issue 4 (17th August 2017)

• Record Type: Journal Article
• Authors: Kitagawa, Ryo; Ueno, Mitsuru; Masaki, Takashi
• Editors: Verheyen, Kris
• Is Part Of: Applied vegetation science. Volume 20:Issue 4(2017:Oct.)
• Page Start: 673
• Page End: 682
• Publication Date: 2017-08-17
• Subjects: Beta‐diversity -- Biodiversity conservation -- Canopy thinning -- Community assembly -- Forest management -- Japanese cedar -- Monoculture plantation forest -- Understorey woody plant community; Plant ecology -- Periodicals; Plant communities -- Periodicals; Plant populations -- Periodicals; Nature -- Effect of human beings on -- Periodicals; 581.705
• DOI: 10.1111/avsc.12327
• Languages: English
• ISSNs: 1402-2001

Abstract

Abstract: Aim: To maintain biodiversity in plantation forest ecosystems it is important to understand the community assembly process. Canopy thinning effectively increases understorey diversity in plantation forests. However, the process of understorey community assembly after canopy thinning remains unclear. We compared the relative importance of two mechanisms that could affect the assembly of understorey woody communities after thinning: (1) environmental filtering due to competition from canopy trees, and (2) stochastic immigration. If the latter is dominant, the effectiveness of local treatment might be unpredictable because of the variable probability of immigration at each location. Location: Yamagata Prefecture, Japan. Methods: We censused the understorey tree communities in 18 quadrats (each 1 m × 1 m) in each of 49 stands of Japanese cedar plantations. The mean species richness of the 18 quadrats (alpha‐diversity), variation in community composition among them (beta‐diversity), deviation of beta‐diversity from that of a random community (beta‐deviation) and total species richness of the plots (gamma‐diversity) were compared among censuses (before thinning, 2 and 5 yr after thinning). The relative contributions of two explanatory variables to the various diversities were examined: (1) basal area of canopy trees (overstorey BA, an index of environmental filtering), and (2) available seed source in the surrounding landscape (landscape effect; an index of the probability of immigration). Results: Although neither beta‐diversity nor gamma‐diversity changed throughout the censuses, the alpha‐diversity, stem abundance and beta‐deviation were affected by thinning. beta‐deviation increased after thinning. Overstorey BA limited alpha‐ and gamma‐diversity throughout the censuses. The landscape effect was more significant in terms of beta‐deviation after than before thinning. In addition, the effective scale of the landscape effect increased after thinning. Conclusion: Our results indicate that both processes are important: thinning brought about an increase in the relative importance of stochastic immigration as well as a reduction in competitive pressure from canopy trees. These results suggest that while local treatment can increase understorey diversity, stochastic immigration from seed sources is the direct driver after thinning. Although local treatment is effective, its efficiency depends on the seed source availability in the surrounding landscape. Abstract : How can we increase biodiversity in species‐poor plantation forests? Analyses on community assembly mechanisms can provide a critical step towards answering this question. In this paper, we described the processes through which understory trees of multiple species assemble to Japanese cedar plantations from surrounding landscapes. We discussed possible management schemes based on the theory of community ecology.