No abstract

The giant panda ( Ailuropoda melanoleuca ), now restricted to approximately 24 montane forest areas in southwest China, is one of the world's most imperiled mammals. The Qinling Mountains in Shaanxi Province is refuge to approximately 220 pandas and is the focus of our study. Pandas in the Qinling Mountains are elevational migrants, needing both low‐ and high‐elevation montane forests to survive. The current network of nature reserves provides protection for <50% of their remaining habitat and fails to conserve essential habitat for dispersal. Using a combination of satellite classification, fieldwork, and geographic information system analyses, we identified a landscape, termed a giant panda conservation unit, that would meet the long‐term, elevational requirements for giant pandas in the Qinling Mountains. Our results indicate that although the central portion of the panda's range is well protected, additional protection and several areas providing linkage to adjacent habitat blocks are needed to provide adequate habitat for long‐term survival. Our results could be applied to a wide range of species, such as habitat or dietary specialists, elevational migrants, species at the edge of their historic range, and area‐sensitive species that require winter refugia.

Measurements of photosynthetically active radiation (PAR), leaf photosynthesis, canopy leaf area index (LAI) and crop yield were carried from flowering to maturity to study the effects of tree shading on crop yield in a Paulownia-wheat intercropping system in China. We found that the tree shading reduced the amount of incoming PAR within the intercropping system by 22%, 44% and 56% during flowering, grainfilling and maturing, respectively. The amount of PAR intercepted by the wheat crop inside the intercropping system was 34%, 55% and 68% less than the crop outside the intercropping system during flowering, grain-filling and maturing. Estimates of PAR-saturated leaf photosynthetic rate were not affected by tree shading, and the differences between the wheat yield inside the intercropping system and outside the intercropping system can be explained by the difference in the amount of PAR intercepted. Total grain numbers and grain dry weight per 1000 grains were linearly correlated with the amount of PAR intercepted during 7 days prior to anthesis and during anthesis and grain-filling, respectively. As compared with the wheat crop outside the intercropping system, grain numbers and grain dry weight were reduced by 36% and 25%, respectively. As a result wheat yield inside the intercropping system was 51% lower than that outside the intercropping system. Our results suggest a much higher reduction in crop yield and much smaller economic gain of the Paulownia-wheat intercropping system than previous studies on the similar Paulownia-wheat intercropping systems in China.