Abstract
Understanding the spatial and temporal effects of variable environmental conditions on demographic characteristics is important in order to stop the decline of endangered-species populations. To capture interactions between a species and its environment, in this work the demographic traits of the European ground squirrel (EGS), Spermophilus citellus, were modeled as a function of agricultural landscape structure. The habitat suitability index was determined for 20 localities within the study area based on habitat use, management and type. After mapping the habitat patch occupancy in the field, crop cover maps, the average normalized difference vegetation index (NDVI) and automated water extraction index (AWEI) were obtained from satellite images covering the period 2013-2015. This data was used to develop population-level generalized linear models (GLMs) and individual-level conditional mixed-effects models (GLMMs) in R package Ime4, focusing on the key demographic traits of the EGS. The land composition and patch carrying capacity (PCC) are the key determinants of the endangered EGS population size, while system productivity is the main factor influencing individuals? body condition after monitoring for variations across sampling years and age classes. The proposed landscape structural models show that human activities and abiotic factors shape the demographic rates of the EGS. Thus, to conserve threatened species, an appropriate focus on the spatial adaptation strategies should be employed.
Highlights
In agricultural settings, open grassland ecosystems host a significant number of species and have been recognized among the most threatened ecosystems on the planet [1]
The local corridor comprises a mosaic of steppe grasslands, saline soils/depressions and salt steppe ecosystems [2]. This is a highly important conservation area designated for providing protection to certain groups of species, plant communities and host sites recognized as protected areas, Important Bird Areas (IBA) [15], Important Plant Areas (IPA) [16], Emerald [17] and Ramsar [18] sites [10]
Global generalized linear models (GLMs), which includes all three components (Category 1, 2 and 3) of landscape structure, provided the best fit to the data pertaining to population growth (Table 1)
Summary
Open grassland ecosystems host a significant number of species and have been recognized among the most threatened ecosystems on the planet [1]. The grasslands at the southern edge of the Pannonian Basin (e.g., the region of Vojvodina Province in Serbia) are affected by agricultural intensification and land use degradation as a consequence of adverse local and regional agricultural policies [2]. Increased fragmentation has resulted in the isolation of populations of many species and has reduced habitat availability. EGS is a grassland specialist, inhabiting a variety of natural, semi-natural and artificial open grassland habitats across its range [6]. Its numbers are in continuous decline, especially in the southern, northern and northwestern parts of
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