Fine-scale characteristics of the boundaries between annual patches and perennial patches in a meadow steppe

Abstract

Context Boundaries are ubiquitous and may have crucial influence on the pattern, process, and dynamics of landscapes. However, there is little understanding of mechanisms that govern changes in the location and composition of boundaries. Especially, it is still uncertain whether there are definite relationships between vegetation and soil. At smaller scales, investigation of more detailed soil and vegetation characteristics can more clearly reveal the linkages between soil properties and vegetation patterns. Objectives We studied fine-scale characteristics of boundaries between two physiognomically distinct patch types, annual patches and perennial patches, in a saline-alkaline grassland. The aims were to examine the relationship between vegetation patterns and soil properties, and to explore mechanisms that govern changes in the location and composition of boundaries. Methods In a 50 ha grassland fenced for more than ten years and where a recovery process had been initiated and where annual grasses were dominating in most salinealkaline areas, we quantitatively characterized the spatial gradients across the visually-identified physiognomic boundary (subsequently adjusted by hierarchical clustering approach) between the annual patches and perennial patches at a fine spatial scale (220 cm × 50 cm transects consisting of 11 quadrats). We statistically defined the boundaries by the Split Moving Window method based on soil and plant variables. We also applied Canonical Correspondence Analysis and Nonmetric Multidimensional Scaling to assess the relationship between the fine-scale functional 3 patterns and soil properties along the studied environmental gradient. Results At fine scale, the vegetation and soil boundaries were well-defined and statistically characterized by a high rate of change, compared to the immediately adjacent areas. The plant characteristics were markedly influenced by soil properties. The alteration of salinity and alkalinity were the most important factors explaining the plant patterns across the patch boundaries. However, physiognomic vegetation boundaries did not fully coincide with the soil boundaries, nor with statisticallydefined boundary in species richness and biomass. There were successional processes of colonization involved in perennials encroachment in the annual patches. Conclusions Underlying soil properties primarily determine the plant patterns of the boundary; the plant succession caused by interspecific competition is superimposed on the plant-soil feedback loop maintaining soil nutrient conditions. These processes ultimately alter the characteristics and locations of patch boundaries in response to changing disturbance regimes. Our findings offer insight into the processes occurring at the boundary and how the boundary may respond to the changes of environmental conditions and drive landscape-level dynamics.

Fine-scale analysis of edge effect of shrub patch in different grassland types

“…These results are similar to those found in previous studies of soil and vegetation indicators at the boundary (Cao et al, 2019, Maas et al, 2016. Meanwhile, the results of this study found that the changes in vegetation richness were most influenced by organic matter, and the changes in vegetation richness and organic matter were completely consistent in all types of grasslands (Figure 2A, Figure 3D).…”

“…These patches of vegetation provide a good environment for the study of micro-scale edge effects, all biotic and abiotic factors, and the small dynamics of their relationship with the environment are highly relevant, this relationship can greatly affect the vegetated landscape in the study area, resulting in a landscape pattern that now varies in patch size. (Ferro and Morrone, 2014;Oliveras and Malhi, 2016;Cao et al, 2019). And this association will have a great impact on the vegetation landscape in the study area, resulting in the formation of the current patch size of the landscape pattern.…”

“…The mesoscale edge effect usually refers to the interlacing zone of two ecosystems (Ting and Shaolin, 2008), which is usually the region with the most abundant biodiversity, and the mesoscale edge effect is also the region with the most studies at present. There have been extensive studies on forest grassland and grass-thicket edge effects (Bai et al, 2015;Cao et al, 2019). It was found that species diversity usually increases in areas where different ecosystems intersect, while other indicators fall between the two ecosystems (Erdős et al, 2019).…”

“…Within a defined area, changes in boundary effects can lead to changes in many other properties within this area, for example, Y.H. Cao et al (Cao et al, 2019) scholars have studied annual and perennial patches within saline lands in the Northeast. The results showed that the changes in species richness and coverage of vegetation patches were obviously influenced by soil changes, but the changes were not consistent with all soil changes.…”

Partitioned beta diversity patterns of plants across sharp and distinct boundaries of quartz habitat islands

“…In contrast, we investigated much smaller-scaled boundaries on the quartz islands of our study area, where microscale soil heterogeneity reflects the spatial distribution of vegetation communities (Schmiedel et al, 2015) and seems to be the principal abiotic factor shaping diversity patterns. Studies investigating the sharp plant species turnover caused by small-scale edaphic gradients are scarce, presumably because transition types with this grain size seem to occur mainly on sites with special soils in semi-arid or arid environments such as gypsum (Rubio & Escudero, 2000) or serpentine (Harrison et al, 2006); or saline/alkaline soils in grasslands (Cao et al, 2019).…”