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Left to right: Data collection using single rope climbing technique. Measuring host bark pH, Bulbophyllum affine on Rhododendron arboreum host, Rhynchostylis retusa on Ficus religiosa host tree.
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This dissertation explored the relationships between distribution of epiphytic orchids in relation to habitat and host tree characteristics on a gradient of different land-use intensities in Kathmandu Valley to support development of conservation management approaches.
Firstly, this thesis started with distribution pattern of Rhynchostylis retusa...
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Citations
... However, Ficus religiosa, Alnus nepalensis, and Schima wallichii are the most common and suitable host tree species (Raskoti 2009;Adhikari and Fischer 2011;Adhikari et al. 2012). Rhynchostylis retusa is found on hosts, which have high bark pH, receive fairly intermediate sunlight intensity, are tall, and have a large trunk diameter at breast height (Adhikari 2013, Adhikari et al. 2016. The orchid is an ecologically opportunistic species and able to occur also in disturbed areas (i.e., intensive land use area; urban areas). ...
... The orchid is an ecologically opportunistic species and able to occur also in disturbed areas (i.e., intensive land use area; urban areas). Small old tree patches, isolated trees in urban areas also provide good habitat and are crucial for R. retusa (Adhikari 2013(Adhikari , 2016. Parab and Krishnan (2008) found that R. retusa has high genetic variability within populations even in small study regions. ...
Rhynchostylis retusa(L.) Blume:Aerides guttata (Lindl.) Roxb.; Aerides praemorsa Willd.; Aerides retusa (L.) Sw.; Aerides spicata D. Don; Aerides undulata Sm.; Epidendrum hippium Buch.-Ham. ex D. Don; Epidendrum indicum Poir.; Epidendrum retusum L.; Gastrochilus blumei (Lindl.) Kuntze; Gastrochilus retusus (L.) Kuntze; Gastrochilus rheedei (Wight) Kuntze; Gastrochilus spicatus (D. Don) Kuntze; Limodorum retusum (L.) Sw.; Orchis lanigera Blanco; Rhynchostylis albiflora I. Barua & Bora; Rhynchostylis garwalica (Lindl.) Rchb. f.; Rhynchostylis guttata (Lindl.) Rchb. f.; Rhynchostylis praemorsa (Willd.) Blume; Rhynchostylis retusa f. albiflora (I. Barua & Bora) Christenson; Saccolabium blumei Lindl., Saccolabium furcatum B. S. Williams; Saccolabium garwalicum Lindl.; Saccolabium macrostachyum Lindl.; Saccolabium praemorsum (Willd.) Lindl.; Saccolabium retusum (L.) Voigt; Saccolabium rheedei Wight; Saccolabium spicatum (D. Don) Lindl.; Sarcanthus guttatus Lindl.
... We assigned each epiphyte individual to one of three predefined tree layers, following a modification of the Johansson's scheme (Zotz, 2007;Adhikari, 2013): layer 1 (the trunk up to the first branch), layer 2 (lower canopy layer) and layer 3 (upper canopy layer, if the tree height is 15 m then the upper 1/3 of the tree canopy, and if the tree height is less than 15 m then it is divided into three equal tree layers). We aggregated Johansson's scheme into these three layers because a more detailed tree layer separation was simply not applicable due to the complex tree architecture encountered in the field. ...
Epiphytes are one of the most diversified plant life forms, whose species richness peaks in the tropics and subtropics. Here we examined the vertical distribution metrics (i.e., number of epiphyte individuals and epiphyte species richness) of vascular epiphytes (orchids and ferns) on two dominant host trees (Schima wallichii (DC.) Korth. and Quercus lanata Sm.) in sub-tropical forests of Nepal. We sampled a total number of 72 host trees of Q. lanata and S. wallichii from two forest sites: a government protected national park forest and community managed forest. We applied generalized linear mixed models and Kruskal-Wallis rank sum tests to explain epiphyte diversity by tree architecture (i.e., diameter at breast height, tree height, crown size, number of forks, bark rugosity, bark pH and tree layer), host species and forest management types. After variable selection via multi-model inference technique, we found diameter at breast height to be the most powerful and significant explanatory variable for the number of epiphyte individuals and epiphyte species richness across host tree species, tree layers, and forest management types. Interestingly, epiphyte diversity was on average higher in the community managed forest than in the national park forest,on S. wallichii than on Q. lanata and particularly on the trunk below forks. We conclude that effective conservation of epiphyte diversity in the Nepal Himalaya requires conservation of old-growth host trees through community approaches. If large and old tree stands are maintained, community managed forests can host high diversity of vascular epiphytes and provide ecosystem goods to local people alike.
... However, Ficus religiosa, Alnus nepalensis, and Schima wallichii are the most common and suitable host tree species (Raskoti 2009;Adhikari and Fischer 2011;Adhikari et al. 2012). Rhynchostylis retusa is found on hosts, which have high bark pH, receive fairly intermediate sunlight intensity, are tall, and have a large trunk diameter at breast height (Adhikari 2013, Adhikari et al. 2016. The orchid is an ecologically opportunistic species and able to occur also in disturbed areas (i.e., intensive land use area; urban areas). ...
... The orchid is an ecologically opportunistic species and able to occur also in disturbed areas (i.e., intensive land use area; urban areas). Small old tree patches, isolated trees in urban areas also provide good habitat and are crucial for R. retusa (Adhikari 2013(Adhikari , 2016. Parab and Krishnan (2008) found that R. retusa has high genetic variability within populations even in small study regions. ...
... Host position and type (Flores-Palacios and García-Franco 2006;Hirata et al. 2009;Timsina et al. 2016), as well as the growth of epiphytic species, are influenced by different environmental factors such as annual precipitation, light intensity, humidity Werner and Gradstein 2009), aspect (Adhikari et al. 2015;Timsina et al. 2016), climatic conditions (Callaway et al. 2002;Adhikari et al. 2012b;Adhikari et al. 2016), site variation (Otero et al. 2007, microsite conditions (Graham and Andrade 2004;Adhikari et al. 2012a), host tree size (Wolf 2005;Flores-Palacios and García-Franco 2006;Adhikari et al. 2012b), bark roughness (Callaway et al. 2002;Adhikari et al. 2012a;Adhikari et al. 2012b;Timsina et al. 2016), and bark pH (Adhikari et al. 2015). Moreover, the quality of the microhabitat of epiphytic plant species is especially important for germination and establishment (Turner et al. 1994;Ackerman et al. 1996;Adhikari et al. 2012a;Adhikari et al. 2012b;Adhikari 2013;Wagner et al. 2015). As shown by studies of tropical and subtropical forests (Wolf and Flamenco-S 2003), even the general climate type (for example, lowland tropical to mountain temperate) influences the species richness and distribution of epiphytic vegetation. ...
Abstract
Epiphytic plant species are an important part of biological diversity. Therefore, it is important to understand the distribution patterns of epiphytic plants and the factors influencing these patterns with regard to environmental conditions, natural biotic interactions and human influences (utilization) in detail to develop conservation strategies. We aimed to better understand the patterns of species richness, abundance and composition of epiphytic orchid and fern species in two subtropical forests in Nepal. We also studied the relationship between host (Schima wallichii and Quercus lanata) and epiphyte species. Data were collected in the Naudhara community forest (CF) and the national forest (NF) in the Shivapuri Nagarjun National Park. The data were analyzed using univariate and multivariate tests. In total, we recorded 41 species of epiphytes (33 orchid and 8 fern species).
Orchid species abundance was significantly higher in the CF than in the NF, but there was no corresponding pattern for fern species. Orchid species richness and abundance increased with increasingly southern aspects. However, orchid species richness decreased with increasing canopy cover, and fern species richness increased with host bark roughness. Orchid species abundance was positively correlated with increasing bark pH, stem size, tree age and tree height and negatively correlated with increasing steepness of the area. Likewise, fern abundance was high in places with high canopy cover and trees that were tall and with a larger stem size but decreased with increasing altitude and southern aspect. Orchid abundance was higher on S. wallichii than on Q. lanata trees. The composition of the orchid and fern species was influenced by altitude, aspect, canopy cover, DBH, tree fork number and forest management types.
The orchid patterns found in the two differently managed forest types differed significantly: the community forest, which has been recently managed, hosts more epiphytic orchid species than the national forest, which has been protected for approximately two decades but had been previously used intensively. Epiphytic ferns, in contrast, did not show similar patterns because in the managed community forest, old and large tree individuals are allowed to survive. The park’s protected status (e.g., as a national park), granted two decades after its foundation, was not as important for the epiphytes as were elements of naturalness, especially large (and usually old) trees. In terms of protecting nature, this means that long-term protection of epiphyte biodiversity can be combined with forest utilization, as long as some large trees are allowed to survive (and smaller ones are allowed to grow larger). Some epiphytes showed a preference for one of the studied host tree species.
We conclude that the diversity of orchid and fern epiphytes is influenced by host characteristics as well as host types. The most important prerequisite for high epiphyte biodiversity is the presence of old, tall trees, independent of a site’s recent protection status. This means that (i) for protection, e.g., national park designation, areas that host old, tall trees should be selected; and (ii) epiphytes can be protected in managed forests and even in intensively used landscapes by leaving a certain number of trees alone and by giving them the space to grow old and tall.
Keywords: Environmental factors; Epiphytes; Large trees; Indicator species; Multivariate and univariate analyses; Permutations tests
... R. australis) and microhabitat resource availability of hosts are presumed to be important in the establishment of resident epiphytes. The occurence and density of epiphytes are influenced by host characteristics (host bark, pH, water holding capacity of bark and bark rugosity), which play importent role in determining aggregation and abundance of epiphyte species (Adhikari 2013). It is also reported that some epiphyte species show a preference for particular host and host traits (Hirata et al. 2009). ...
Vascular epiphytes live non-parasitically on other plants and are a distinctive and intergral component of tropical forests. There is a general lack of studies examining epiphyte diversity in urban settings. The aim of this study was to document the diversity of epiphytes on host trees in the eThekwini Metropolitan Area (EMA). In addition, the number of individuals of each epiphyte, host tree circumference at breast height and height were recorded. In total, 30 epiphyte species from 12 families were recorded, with most epiphyte species belonging to the Moraceae (n = 8) and Araliaceae (n = 5). A total of 34 host species from 15 families were recorded. These numbers did not increase when considering herbarium material within the EMA sensu stricto. The highest epiphyte richness (n = 13) was reported on the palm Raphia australis. The high number of both alien host and epiphytic taxa are of concern. More studies are needed to understand how epiphyte/host interactions in the urban landscape are established and maintained.
The survival chance of epiphytic orchids today not only depends on the natural site conditions required by the orchids but also on anthropogenic changes in site conditions. This study answers two questions: (1) What is the ecological niche of the different epiphytic orchid species? (2) What are the ecological factors that threaten epiphytic orchid’s population under anthropogenic disturbances? Our study area was the Kathmandu valley, Nepal, with its subtropical forest. We established 156 systematically selected sampling points in the Kathmandu area covering different types of ecosystems under human impacts such as densely populated area, agricultural land, mixed agricultural and settled area old tree patches, and a natural forest in a national park. The ecological niche of the orchid species was analyzed with a principal component analysis (PCA). The correlations between the different site factors were statistically significant. Spearman’s rank correlation matrices showed that the variables land-use intensities with altitude, and height with diameter in breast height (dbh) of host had the highest significant positive correlation coefficient (0.67 and 0.64 respectively). On the other hand, host bark pH and altitude as well as land use had a significant very strong negative correlation coefficient (-0.80 and -0.61, respectively). Different epiphytic orchid species interact differently with the given set of environmental factors: for occurrence of Vanda cristata there is no single environmental factor of special influence, while for Rhynchostylis retusa high bark pH and high light availability are important. PCA explained more than 50% of the total variance. Most orchid species occupy a specific, narrow niche in this ecological space. The main causes of anthropogenic influence of orchid population in the Kathmandu Valley are loss of adequate host trees (species and size) and increasing air pollution, resulting in increasing host bark pH.
