Monitoring Forest Cover Change and Fragmentation Using Remote Sensing and Landscape Metrics in Nyungwe-Kibira Park

The objective of this study was to evaluate forest cover change and forest degradation in Nyungwe-Kibira Park, a natural reserve straddling Rwanda and Burundi from 1986 to 2015. Landsat TM, ETM+ and 8OLI images of 30 m spatial resolution were used as primary datasets. Geographic Information System (GIS) techniques were used for forest cover mapping and landscape metrics were calculated by using FRAGSTATS software. Classification and change analysis of forest cover type and landscape patterns analysis were carried out. In addition, to analyze the correlated external disturbances, the buffer zone of 5 Km was delineated outside the boundary of Nyungwe-Kibira Park. The results revealed that in among 5 land cover classes considered within the Park, the dominant one was dense forest class covering over 70% of the entire Park area while in the buffer zone cultivated and open land dominated at over 90% between the years 1986 and 2015. Change detection highlighted that within Nyungwe-Kibira forest, approximately 0.27% (4.97 Km2) of forest cover was cleared while 0.07% (1.22 Km2) was regenerated annually. In the buffer zone, the annual cleared forest cover was about 0.76% (13.02 Km2). The five landscape indices chosen at class level indicated a considerable fragmentation of forest inside the Park and the highest fragmentation in the buffer zone. Indeed, these results shed a bleak image over the future of the Nyungwe-Kibira forest that should be helpful for the policy-makers and managers of these natural parks to establish adequate policies to mitigate the forest loss and degradation by implementing quick and effective solutions.

Analysis of Ecological Environment Changes in Linze from 2000 to 2017 Based on Remote Sensing Images

With the support of RS and GIS technology,the ecological environment of Linze was evaluated and the changes of ecological environment were analyzed from the spatial scope of ecosystem with the remote sensing images in 2000 and 2017 as the information source.The results showed that the areas with excellent,relatively good and relatively poor ecological environment in Linze showed a decreasing trend from 2000 to 2017,which decreased by 262.50,7,156.25 and 12,256.30 hm^2,respectively.From the landscape patch pattern,the patch density in areas with relatively good ecological environment increased the fastest from 2000 to 2017,which was 13.05 pieces/hm^2.The largest plaque index in areas with relatively good ecological environment decreased by 1.314%,and the dominance of large plaque in the region decreased.The assessment results of ecological environment based on remote sensing demonstrated that the ecological environment in Linze was generally healthy from 2000 to 2017,and the deterioration was improved.Among them,the area transformed from relatively poor ecological environment to other types was the largest,which was 17,512.92 hm^2,and the proportion of the area transformed into general ecological environment was the highest,accounting for 80.7%of the transformed area of the region.

Assessment of tectonic control on the development of low mountains moderate relief in the Outer Carpathians(Southern Poland)

Inherited tectonic structures,ongoing tectonic deformation,and variations in relative rock uplift rates play an important role in conditioning the processes of relief development.Their influence among other factors,such as climate and lithology,can be quantified using landscape analysis,and geomorphometric indices,in particular.The usage of landscape analysis in recent years is increasing systematically due to the constant improvement of the digital elevation models and GIS software that significantly facilitate this approach.In this study,we aim to recognize the influence of tectonic structures and processes on relief development in the low mountains with moderate relief of the Sola River catchment in the Western Outer Carpathians.To this end,we calculated geomorphometric indices(river longitudinal profile,stream-length gradient index,minimum bulk erosion,relief ratio,circulatory ratio,elongation ratio,and hypsometric integral)for the Sola River and its 47 sub-catchments using a 25-m spatial resolution Digital Terrain Elevation Data Level 2.Additionally,we identified lineaments and knickpoints and correlated the computed results with local and regional fault networks,variations in lithology,and climate fluctuations.Obtained results indicate a significant impact of inherited tectonicstructures on the relief development of the Sola River catchment,i.e.,directions of principal ridges and valleys follow the orientation of main folds and faults recorded in this area.Anomalously high values of minimum bulk erosion,river gradient,and streamlength gradient index allowed us to define two areas with higher relative uplift rates:1)the So?a Gorge and 2)the Beskid Zywiecki Mts.Polish Outer Carpathians are generally considered as an area of low strain rate and low seismic activity.However,the possibility of neotectonic processes should be considered in geohazard estimations.Observed bends in the direction of river valleys that do not correspond with changes in lithology could be related to active strikeslip faults.These are probably the reactivated basement structures,copied in the thin-skinned nappe cover,as a result of the accommodation of the Mur-Zilina Fault Zone resulting from the tectonic push of the Alcapa(Alpine-Carpathian-Pannonian)microplate against the European plate.Thus,the role of recent tectonic activity in relief development of the Sola River catchment even though appears to be subsidiary at the most,should not be excluded.

The effect of water spreading system on the functionality of rangeland ecosystems

In recent decades, the control of floods is an efficient management practice for the rehabilitation of rangelands in most arid and semiarid areas. To evaluate the benefits, we used the Landscape Function Analysis （LFA） method to assess the function of patches and qualitative capability of a rangeland ecosystem in Gareh By- gone region, Fars province, southwestern Iran. Landscape functionality depends on soil, water and nutrient （col- lectively called ＂resources＂） conservation and use within a given ecosystem. Many landscapes are naturally het- erogeneous in terms of resource control and possess patches, where resources tend to accumulate, and in- ter-patches. Assessing rangeland health and function of landscape patches in response to environment and man- agement can give rise to correct management decisions for qualitative improvement of the ecosystem. Therefore, our study area was divided into two parts, i.e. water spreading and control parts, and sampling was done using LFA method in each part separately. Structural parameters, including the number, length and width of patches, and the mean length of inter-patches, were determined by the method to characterize the functional status of the monitoring sites. For each patch/inter-patch type identified in the transect organization log, we recorded its soil surface proper- ties classified according to the Soil Surface Assessment Method. The density, canopy cover and composition of plants were then assessed. The results showed that the number of ecological patches and their dimensions were significantly increased in the water spreading site. Soil stability and the values of nutrient cycling indices were in- creased but the infiltration values were decreased in the water spreading site. It could be related to the effect of suspended materials transported by floods to the soils in the study area. The improvement of ecological patches and rangeland ecosystem was achieved where water spreading systems were practiced. Therefore it can be con- cluded that water spreading as a management plan plays an important role in arid land ecosystem functionality.

Landscape spatial configuration is a key driver of wild bee demographics

The majority of studies investigating the effects of landscape composition and configuration on bee populations have been conducted in regions of intensive agricultural production, ignoring regions which are dominated by seminatural habitats, such as the islands of the Aegean Archipelago. In addition, research so far has focused on the landscape impacts on bees sampled in cropped fields while the landscape effects on bees inhabiting seminatural habitats are understudied. Here, we investigate the impact of the landscape on wild bee assemblages in 66 phryganic （low scrubland） communities on 8 Aegean islands. We computed landscape metrics （total area and total perimete^area ratio） in 4 concentric circles （250, 500, 750, and 1000 m） around the center of each bee sampling site including 3 habitat groups （namely phrygana, cultivated land, and natural forests）. We further measured the local flower cover in 25 quadrats distributed randomly at the center of each sampling site. We found that the landscape scale is more important than the local scale in shaping abundance and species richness of bees. Furthermore, habitat configuration was more important than the total area of habitats, probably because it affects bees＇ movement across the landscape. Phrygana and natural forests had a positive effect on bee demographics, while cultivated land had a negative effect. This demonstrates that phryganic specialists drive bee assemblages in these seminatural landscapes. This finding, together with the shown importance of landscape scale, should be considered for the management of wild bees with special emphasis placed on the spatial configuration of seminatural habitats.

The Global Landscape of Phase Retrieval I:Perturbed Amplitude Models

A fundamental task in phase retrieval is to recover an unknown signal x∈R^(n) from a set of magnitude-only measurements y_(i)=|〈a_(i),x〉|,i=1,…,m.In this paper,we propose two novel perturbed amplitude models(PAMs)which have a non-convex and quadratic-type loss function.When the measurements a_(i)∈R^(n) are Gaussian random vectors and the number of measurements m≥Cn,we rigorously prove that the PAMs admit no spurious local minimizers with high probability,i.e.,the target solution x is the unique local minimizer(up to a global phase)and the loss function has a negative directional curvature around each saddle point.Thanks to the well-tamed benign geometric landscape,one can employ the vanilla gradient descent method to locate the global minimizer x(up to a global phase)without spectral initialization.We carry out extensive numerical experiments to show that the gradient descent algorithm with random initialization outperforms state-of-the-art algorithms with spectral initialization in empirical success rate and convergence speed.

The Global Landscape of Phase Retrieval Ⅱ:Quotient Intensity Models

A fundamental problem in phase retrieval is to reconstruct an unknown signal from a set of magnitude-only measurements.In this work we introduce three novel quotient intensity models(QIMs) based on a deep modification of the traditional intensity-based models.A remarkable feature of the new loss functions is that the corresponding geometric landscape is benign under the optimal sampling complexity.When the measurements ai∈Rn are Gaussian random vectors and the number of measurements m≥Cn,the QIMs admit no spurious local minimizers with high probability,i.e.,the target solution x is the unique local minimizer(up to a global phase) and the loss function has a negative directional curvature around each saddle point.Such benign geometric landscape allows the gradient descent methods to find the global solution x(up to a global phase) without spectral initialization.