Plant diversity increases spatial stability of aboveground productivity in alpine grasslands

Plant diversity can significantly affect the grassland productivity and its stability. However, it remains unclear how plant diversity affects the spatial stability of natural grassland productivity, especially in alpine regions that are sensitive to climate change. We analyzed the interaction between plant (species richness and productivity, etc.) and climatic factors (precipitation, temperature, and moisture index, etc.) of alpine natural grassland on the Qinghai-Tibetan Plateau. In addition, we tested the relationship between plant diversity and spatial stability of grassland productivity. Results showed that an increase in plant diversity significantly enhanced community productivity and its standard deviation, while reducing the coefficient of variation in productivity. The influence of plant diversity on productivity and the reciprocal of productivity variability coefficient was not affected by vegetation types. The absolute values of the regression slopes between climate factors and productivity in alpine meadow communities with higher plant diversity were smaller than those in alpine meadow communities with lower plant diversity. In other words, alpine meadow communities with higher plant diversity exhibited a weaker response to climatic factors in terms of productivity, whereas those with lower plant diversity showed a stronger response. Our results indicate that high plant diversity buffers the impact of ambient pressure (e.g., precipitation, temperature) on alpine meadow productivity, and significantly enhanced the spatial stability of grassland productivity. This finding provides a theoretical basis for maintaining the stability of grassland ecosystems and scientifically managing alpine grasslands under the continuous climate change.

Delineation of basic farmland based on the quality and spatial stability: a case study of Yingtan City, China

Delimiting basic farmland is essential to ensure food security and maintain social stability. Determining the quantity and spatial layout of the basic farmland is the main aspect of delimitation. For a long time, superiors in local governments have mainly assigned the basic farmland quantity, which is prone to regional imbalance. The determination of the spatial layout is mainly based on the quality and contiguity of the cultivated land; however, spatial stability is not considered. Therefore, in this study, Yingtan City was used as an example to determine the scale of basic farmland based on the food security and multi-source data, construct a Land Evaluation and Site Assessment System model, evaluate the quality of cultivated land, and integrate the degree of agglomeration and compatibility of cultivated land to characterize its spatial stability. The quality and spatial stability of the cultivated land were combined to construct a matrix. The cultivated land patches must be selected according to the "scale limitation, stability priority, and quality superiority" principle. Finally, basic farmland covering an area of 75,946.34 hm² was delineated, whose average quality index and spatial stability increased by 0.02 and 0.04, respectively. The landscape structure is more stable than the originally planned structure, which is conducive to the sustainable development of the cultivated land ecosystem. That is, a good delimitation effect was achieved, providing a reference for actual delimitation work.

Dominant species' dominant role and spatial stability are enhanced with increasing stocking rate

Stipa breviflora Grisb. (S. breviflora) is a dominant species in the desert steppe of northern China. Its function and role at the plant community level increases with increasing stocking rate. However, the response of spatial stability remains unclear. We selected treatment areas representing no grazing (CK), light grazing (LG), moderate grazing (MG) and heavy grazing (HG) in a long-term grazing experiment (2004-2017) in a S. breviflora desert steppe in Inner Mongolia, northern China. Using a mechanical sampling method, 40 m × 40 m representative sample plots were selected to obtain the height, coverage and density of the S. breviflora population and community, and we computed the standing crop of mechanical sampling quadrats based on a random sample of cutting quadrats. Analysis of standing crop, density of S. breviflora population and its ratio in the plant community showed that the dominant role of S. breviflora population in the plant community increased with increasing grazing intensity, while the spatial stability of S. breviflora population not only had many dimensions, but also many states. The dimension or combination of dimensions of its stability performance and its adaptive state varied under different disturbance intensities and frequencies.

Buildup of spatial information over time and across eye-movements

To interact rapidly and effectively with our environment, our brain needs access to a neural representation of the spatial layout of the external world. However, the construction of such a map poses major challenges, as the images on our retinae depend on where the eyes are looking, and shift each time we move our eyes, head and body to explore the world. Research from many laboratories including our own suggests that the visual system does compute spatial maps that are anchored to real-world coordinates. However, the construction of these maps takes time (up to 500ms) and also attentional resources. We discuss research investigating how retinotopic reference frames are transformed into spatiotopic reference-frames, and how this transformation takes time to complete. These results have implications for theories about visual space coordinates and particularly for the current debate about the existence of spatiotopic representations.