This post features two manuscripts which look at the science of healthy ecosystems.
First, Fei-Hai Yu discusses his paper ‘Understanding the effects of a new grazing policy: the impact of seasonal grazing on shrub demography in the Inner Mongolian steppe’ by Shou-Li Li, Fei-Hai Yu, Marinus J. A. Werger, Ming Dong, Satu Ramula and Pieter A. Zuidema.
Grazing by livestock is a common land use in arid areas, and developing sustainable grazing regimes that conserve vegetation and maintain productivity is highly important in these ecosystems. Over the past decades, China has been suffering from overgrazing-induced desertification and more frequently occurring sand storms, which are causing severe economic losses. The Chinese government is devoting great efforts to stop overgrazing and has implemented a national policy of seasonal grazing since 2003. To evaluate the effectiveness of the new grazing regime, we studied the life history strategies and population dynamics of a dominant shrub, Caragana intermedia, in Northern China by performing a three year demographic monitoring study for seasonally grazed and ungrazed populations. Integral Projection Models (IPMs) were applied for demographic analysis and they found that maximizing adult survival in grazed populations was crucial for population maintenance. Seedling recruitment fluctuated greatly between years, which could potentially affect population growth, especially in very dry years. Therefore, protecting parts of populations from being grazed during such years would allow continued recruitment and maintenance of viable populations. This study suggests that management recommendations should be based both on the vital rates that are mostly affected and on the vital rates that are most important for population growth.
Second, Takehiro Sasaki discusses his paper ‘Vulnerability of moorland plant communities to environmental change: consequences of realistic species loss on functional diversity’ by Takehiro Sasaki, Masatoshi Katabuchi, Chiho Kamiyama, Masaya Shimazaki, Tohru Nakashizuka and Kouki Hikosaka.
Understanding the consequences of realistic species loss on the functioning and persistence of vulnerable ecosystems is key to devising conservation strategies. Yet, many conservation studies have focused primarily on the patterns of biodiversity distribution. In this paper we examined the simulated consequences of realistic species loss on functional diversity in moorland plant communities (see image below) widely interspersed within a subalpine zone in northern Japan. The realistic order of species loss was derived from the nested subset pattern in the communities. At most sites, ordered species loss caused a relatively small decline in functional diversity until a certain number of species was lost and an accelerating decline thereafter, suggesting relatively low initial vulnerability to species loss. At the other sites, however, ordered species loss caused an approximately proportional decrease in functional diversity, suggesting relatively high vulnerability to species loss. The model indicated that sites with higher elevation, higher carrying capacities, or increasing isolation have a shorter functional diversity half-life. The mapping of this index allowed us to identify the geographical distribution of sites of high conservation priority. The methods here can provide urgently needed information to support the prioritization and decision-making involved in conserving ecosystems in the face of global biodiversity loss.