Challenges of the establishment of rubber-based agroforestry systems: Decreases in the diversity and abundance of ground arthropods.

The global land area devoted to rubber plantations has now reached 13 million hectares, and the further expansion of these rubber plantations at the expense of tropical forests will have significant adverse effects on the ecological environment. Rubber-based agroforestry systems are considered a preferable approach for ameliorating the ecological environment. Many researchers have focused on the positive effects of rubber-based agroforestry systems on the ecological environment, while ignoring the risks involved in the establishment of rubber-based agroforestry systems. The present study investigated the effects of different-aged rubber-based agroforestry systems on the abundance and diversity of ground arthropods. It has been observed that the abundance and taxon richness of ground arthropods generally showed no difference when comparing young and mature rubber plantations. The rubber-based agroforestry systems significantly decreased the understory vegetation species, along with the abundance and taxon richness of ground arthropods compared to the same aged-rubber monoculture plantations. In addition, the change in the abundance and taxon richness of ground arthropods was greatly affected by the understory vegetation species and soil temperature. The abundance and taxon richness of ground arthropods decreased with the decrease in number of species of understory vegetation. The study results indicate that the establishment of rubber-based agroforestry systems have adversely affected the abundance and richness of ground arthropods to an extant greater than expected. Therefore, single, large rubber-based agroforestry systems are not recommended, and the intercropping of rubber and rubber-based agroforestry systems must be designed to promote the migration of ground arthropods between different systems.

Photoprotective and antioxidative mechanisms against oxidative damage in Fargesia rufa subjected to drought and salinity.

Drought and salinity are the two most common and frequently co-occurring abiotic stresses limiting plant productivity worldwide, yet it remains unclear whether bamboo species possess effective mechanisms to protect against oxidative damage caused by drought and salinity, either alone or in combination. In this study, we utilised Fargesia rufa Yi, a species important to forest carbon sequestration and endangered giant pandas, to evaluate physiological, biochemical and ultrastructural responses to drought, salinity and their combination. Under drought alone, F. rufa exhibited reduced water loss from leaves, photochemistry inhibition, pigment degradation, reactive oxygen species accumulation, lipid peroxidation, and damage to organelles compared with salinity and combined stress treatments. The superior performance under drought alone was attributed to greater thermal dissipation and the water-water cycle capacities, increased SOD/AsA-GSH cycle enzymes activities, and a favourable redox balance of antioxidants. Therefore, relative to salinity alone and drought+salinity, F. rufa plants under drought exhibit highly efficient mechanisms to protect against oxidative damage, which most likely allow accelerated recovery of photosynthetic plasticity once the stress is removed.