Reclamation history and land use types across multiple spatial scales shape anuran communities in the coastal land reclamation region

Land reclamation is a widely adopted method for managing land shortage and promoting coastal economic development globally. However, its impacts on biodiversity vary based on distinct reclamation histories and land use management strategies in different regions. This study aims to examine the effects of reclamation history and land use types at different spatial scales on anuran communities in coastal reclaimed land, which are an important taxon in the coastal ecosystem. We used visual and acoustic encounter methods to survey anurans in 2016 and 2017 across 20 1-km radius coastal land reclamation landscapes with different reclamation histories (10, 20, and 60 y after reclamation) in Nanhui Dongtan of Shanghai, an important coastal land reclamation region along the Yangtze River Estuary. Landscape variables (farmlands, woodlands, and impermeable surface covers, and the landscape Shannon diversity index) at four different spatial scales (250 m, 500 m, 750 m and 1000 m) and water salinity in each landscape were measured. Our findings reveal differences in anuran communities between study sites with 10, 20, and 60 years of reclamation history. Abundances of the ornamented pygmy frog (Microhyla fissipes) and Beijing gold-striped pond frog (Pelophylax plancyi) in landscapes with a 10-year reclamation history were significantly lower compared to those with histories of 20 and 60 years. Zhoushan toad (Bufo gargarizans) abundance was significantly negatively related to farmland cover at the 1000 m scale and impermeable surface cover at the 250 m scale; Hong Kong rice-paddy frog (Fejervarya multistriata) abundance was significantly positively related to farmland cover at the 1000 m scale; ornamented pygmy frog abundance was positively related to farmland cover at the 1000 m scale; and Beijing gold-striped pond frog abundance was significantly positively and negatively related to the landscape Shannon diversity index at the 1000 m scale and to water salinity, respectively. Amphibians quickly migrated and colonized coastal reclaimed land from older natural lands. However, two anuran species with specific habitat requirements tended to avoid areas with shorter reclamation histories. The single-species models revealed different responses to various land uses at the various scales, which indicated that land use management was important to amphibian conservation in coastal reclamation regions.

Relative effects of urbanisation, deforestation, and agricultural development on mosquito communities

Context

Despite numerous studies that showed negative effects of landscape anthropisation on species abundance and diversity, the relative effects of urbanisation, deforestation, and agricultural development as well as the spatial extent at which they act are much less studied. This is particularly the case for mosquitoes, which are the most important arthropods affecting human health.

Objectives

We determined the scale of effect of these three landscape anthropisation components on mosquito abundance and diversity. We then assessed which landscape variables had the most effect as well as their independent positive or negative effects.

Methods

We used mosquito data collected by Schaffner and Mathis (2013) in 16 sampling sites in Switzerland. We measured forest, urban and agricultural amounts in 485 concentric landscapes (from 150 to 5000 m radius) around each sampling site. We then identified the spatial extent at which each landscape metric best predicted abundance and diversity of mosquito species and compared the effect size of each landscape component on each response variable.

Results

In Switzerland, urbanisation and deforestation have a greater influence on mosquito diversity than agricultural development, and do not act at the same scale. Conversely, the scale of effect on mosquito abundance is relatively similar across the different landscape anthropisation components or across mosquito species, except for Culex pipiens. However, the effect size of each landscape component varies according to mosquito species.

Conclusion

The scale of management must be selected according to the conservation concern. In addition, a multi-scale approach is recommended for effective mosquito community management.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10980-023-01634-w.

Structuring of plant communities across agricultural landscape mosaics: the importance of connectivity and the scale of effect

Background

Plant communities of fragmented agricultural landscapes, are subject to patch isolation and scale-dependent effects. Variation in configuration, composition, and distance from one another affect biological processes of disturbance, productivity, and the movement ecology of species. However, connectivity and spatial structuring among these diverse communities are rarely considered together in the investigation of biological processes. Spatially optimised predictor variables that are based on informed measures of connectivity among communities, offer a solution to untangling multiple processes that drive biodiversity.

Results

To address the gap between theory and practice, a novel spatial optimisation method that incorporates hypotheses of community connectivity, was used to estimate the scale of effect of biotic and abiotic factors that distinguish plant communities. We tested: (1) whether different hypotheses of connectivity among sites was important to measuring diversity and environmental variation among plant communities; and (2) whether spatially optimised variables of species relative abundance and the abiotic environment among communities were consistent with diversity parameters in distinguishing four habitat types; namely Crop, Edge, Oak, and Wasteland. The global estimates of spatial autocorrelation, which did not consider environmental variation among sites, indicated significant positive autocorrelation under four hypotheses of landscape connectivity. The spatially optimised approach indicated significant positive and negative autocorrelation of species relative abundance at fine and broad scales, which depended on the measure of connectivity and environmental variation among sites.

Conclusions

These findings showed that variation in community diversity parameters does not necessarily correspond to underlying spatial structuring of species relative abundance. The technique used to generate spatially-optimised predictors is extendible to incorporate multiple variables of interest along with a priori hypotheses of landscape connectivity. Spatially-optimised variables with appropriate definitions of connectivity might be better than diversity parameters in explaining functional differences among communities.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12862-021-01903-9.