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Silva Fennica 1926-1997
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Silva Fennica vol. 55 no. 4 | 2021

Category: Research article

article id 10515, category Research article
Alwin A. Hardenbol, Anton Kuzmin, Lauri Korhonen, Pasi Korpelainen, Timo Kumpula, Matti Maltamo, Jari Kouki. (2021). Detection of aspen in conifer-dominated boreal forests with seasonal multispectral drone image point clouds. Silva Fennica vol. 55 no. 4 article id 10515. https://doi.org/10.14214/sf.10515
Highlights: Four boreal tree species (Scots pine, Norway spruce, birches and European aspen) classified with an overall accuracy of 95%; Presence of European aspen detected with excellent accuracy (UA: 97%, PA: 96%); Late spring is the best time for species classification by remote sensing; Best time to separate aspen from birch was when birch had leaves, but aspen did not.

Current remote sensing methods can provide detailed tree species classification in boreal forests. However, classification studies have so far focused on the dominant tree species, with few studies on less frequent but ecologically important species. We aimed to separate European aspen (Populus tremula L.), a biodiversity-supporting tree species, from the more common species in European boreal forests (Pinus sylvestris L., Picea abies [L.] Karst., Betula spp.). Using multispectral drone images collected on five dates throughout one thermal growing season (May–September), we tested the optimal season for the acquisition of mono-temporal data. These images were collected from a mature, unmanaged forest. After conversion into photogrammetric point clouds, we segmented crowns manually and automatically and classified the species by linear discriminant analysis. The highest overall classification accuracy (95%) for the four species as well as the highest classification accuracy for aspen specifically (user’s accuracy of 97% and a producer’s accuracy of 96%) were obtained at the beginning of the thermal growing season (13 May) by manual segmentation. On 13 May, aspen had no leaves yet, unlike birches. In contrast, the lowest classification accuracy was achieved on 27 September during the autumn senescence period. This is potentially caused by high intraspecific variation in aspen autumn coloration but may also be related to our date of acquisition. Our findings indicate that multispectral drone images collected in spring can be used to locate and classify less frequent tree species highly accurately. The temporal variation in leaf and canopy appearance can alter the detection accuracy considerably.

  • Hardenbol, University of Eastern Finland, School of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland ORCID ID: https://orcid.org/0000-0002-0615-505X E-mail: alwin.hardenbol@uef.fi (email)
  • Kuzmin, University of Eastern Finland, School of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland; University of Eastern Finland, Department of Geographical and Historical Studies, P.O. Box 111, FI-80101 Joensuu, Finland ORCID ID:E-mail: anton.kuzmin@uef.fi
  • Korhonen, University of Eastern Finland, School of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland ORCID ID:E-mail: lauri.korhonen@uef.fi
  • Korpelainen, University of Eastern Finland, Department of Geographical and Historical Studies, P.O. Box 111, FI-80101 Joensuu, Finland ORCID ID:E-mail: pasi.korpelainen@uef.fi
  • Kumpula, University of Eastern Finland, Department of Geographical and Historical Studies, P.O. Box 111, FI-80101 Joensuu, Finland ORCID ID:E-mail: timo.kumpula@uef.fi
  • Maltamo, University of Eastern Finland, School of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland ORCID ID:E-mail: matti.maltamo@uef.fi
  • Kouki, University of Eastern Finland, School of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland ORCID ID:E-mail: jari.kouki@uef.fi
article id 10441, category Research article
Dipak Mahatara, Amul K. Acharya, Bishnu P. Dhakal, Dipesh K. Sharma, Sunita Ulak, Prashant Paudel. (2021). Maxent modelling for habitat suitability of vulnerable tree Dalbergia latifolia in Nepal. Silva Fennica vol. 55 no. 4 article id 10441. https://doi.org/10.14214/sf.10441
Highlights: Dalbergia latifolia is a vulnerable species of Nepal with very few conservation priorities; Habitat suitability modelling for this species is essential to endorse different conservation interventions; 43 presence locations and different environmental variables were retained for model prediction in Maxent; Province 2 was found most suitable habitat for the growth of D. latifolia, with western most province as unsuitable.

Dalbergia latifolia Roxb., commonly known as rosewood, is one of the highly valuable tropical timber species of Nepal. The tree species was widely distributed in the past, however, over-exploitation of natural habitat, deforestation, forest conversion for agriculture, illegal logging and the invasion of alien species resulted in the classification of this species as vulnerable by the IUCN (International Union for Conservation of Nature) category. So, the prediction of habitat suitability and potential distribution of the species is required to develop restoration mechanisms and conservation interventions. In this study, we modelled the suitable habitat of D. latifolia over the entire possible range of Nepal using a Maxent model. We compiled 23 environmental variables (19 bioclimatic, 3 topographic and a vegetative layer), however, only 12 least correlated variables along with 43 spatially representative presence locations were retained for model prediction. We used a receiver operating characteristic (ROC) curve to assess the model’s performance and a Jackknife procedure to evaluate the relative importance of predictor variables. The model was statistically significant with an area under the curve (AUC) value of 0.969. The internal Jackknife test indicated that elevation was the most important variable for the model prediction with 71.3% contribution followed by mean temperature of driest quarter (9.8%). The most (>0.6) suitable habitat for the D. latifolia was 235 484 hectares with large sections of area in two provinces whereas, the western most provinces were not suitable for D. latifolia as per Maxent model. The information presented here can provide a framework for nature conservation planning, monitoring and habitat management of this rare and endangered species.

  • Mahatara, Forest Research and Training Centre, Government of Nepal, P.O. Box 3339, Babarmahal, Kathmandu 44600, Nepal ORCID ID:E-mail: honeystar73@gmail.com (email)
  • Acharya, Forest Research and Training Centre, Government of Nepal, P.O. Box 3339, Babarmahal, Kathmandu 44600, Nepal ORCID ID:E-mail: acharya.amulkumar@gmail.com
  • Dhakal, Forest Research and Training Centre, Government of Nepal, P.O. Box 3339, Babarmahal, Kathmandu 44600, Nepal ORCID ID:E-mail: dhakalbp.shorea@gmail.com
  • Sharma, Forest Research and Training Centre, Government of Nepal, P.O. Box 3339, Babarmahal, Kathmandu 44600, Nepal ORCID ID:E-mail: dipeshsharmadiyu2015@gmail.com
  • Ulak, Forest Research and Training Centre, Government of Nepal, P.O. Box 3339, Babarmahal, Kathmandu 44600, Nepal ORCID ID:E-mail: sunitaulak@gmail.com
  • Paudel, Agriculture Forestry University, P.O. Box 13712 Rampur, Chitwan, Nepal ORCID ID:E-mail: prashant.paudel88@gmail.com

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