This post features three manuscripts which look at managing impacts of land use change.
First, Kei Uchida discusses his paper ‘Land abandonment and intensification diminish spatial and temporal β-diversity of grassland plants and herbivorous insects within paddy terraces’ by Kei Uchida and Atushi Ushimaru.
Semi-natural grasslands on the paddy field margins, which are maintained by periodic mowing, harbour high biodiversity in Japan. When farmers manage agricultural lands using traditional management practices (i.e. through an intermediate disturbance), high biodiversity and biological heterogeneity would be maintained. However, recently, biodiversity has rapidly declined due to land-use changes (changes in mowing frequency and landscapes) in Japanese agricultural lands. Our study showed that extensive traditional management enhances the spatio-temporal heterogeneity of diversity at within-field scale, with high biodiversity; however, these practices have been ceased due to land-use changes in rural areas. We suggest that traditional management practices are essential to conserve species pools in agro-ecosystems.
Japan is considered as a global hotspot of biodiversity (Conservation International 2015); however, land-use changes have rapidly driven loss of biodiversity in semi-natural grasslands (Uchida & Ushimaru 2014, 2015). And, over the past century, semi-natural grasslands have rapidly declined from approximately 5,000,000 ha to 430,000 ha (<10 % remaining), severely limiting habitats for numerous grassland species. The effects of land-use changes on biodiversity in semi-natural grasslands have not received much attention in East Asia and for future study, we should examine different agricultural systems in other East Asian regions as well as worldwide.
Second, Han Xu discusses his paper ‘Partial recovery of a tropical rain forest a half-century after clear-cut and selective logging’ by Han Xu, Yide Li, Shirong Liu, Runguo Zang, Fangliang He and John R. Spence.
To what extent can logged rainforests recover after a half-century? We found that a rainforest can only partially recover the characteristics of primary forest a half-century after logging in Jianfengling, Hainan Island, China. Although species richness recovered fast, recovery of the original tree biodiversity will be slow at best, if measured by species composition or stand structure. Within 20–40 years is the critical stage for the recovery of logged forests. In our study we found that shortly after harvest, pioneer species increased rapidly, but shade-tolerant species required much more time to recover to former abundances. Selectively logged forests recovered more quickly and had higher conservation values than clear-cut forests. This study amplifies the importance of conserving tropical rainforest integrity and developing harvest and management approaches that facilitate full recovery of logged tropical rainforests.
Lastly, Wenying Jiang discusses her paper ‘Chinese Loess Plateau vegetation since the Last Glacial Maximum and its implications for vegetation restoration’ by Wenying Jiang, Yufen Cheng, Xiaoxiao Yang and Shiling Yang.
Destruction of vegetation cover on the vast Chinese Loess Plateau (~440,000 km2) has resulted in severe soil erosion. To tackle this issue, China has been investing heavily in numerous afforestation programmes. However, excessive reliance on afforestation has caused significant negative environmental impacts. A major reason for the failure of afforestation is the use of inappropriate species because of a lack of knowledge of the natural vegetation, which has been largely destroyed by human activities.
Based on pollen analyses of six loess sections, we found that the natural vegetation on the Plateau consists mainly of herbs at least for the past ~28,000 years. Therefore, priority should be given to planting herbs rather than trees or shrubs in the area in current and future greening programmes. To combine ecological restoration with economic growth, walnut, hazelnut and some medicinal plants should also serve as useful candidate species for the south-eastern Loess Plateau. In addition, given the considerable prevalence of Chinese spikemosses and the daisy family in the pollen records, and their useful medicinal effects, the Loess Plateau has great potential to be a centre for Chinese medicinal herb production.