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- Taylor & Francis
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- © 2015 Taylor & Francis
- ISSN
- 2151-3732
- eISSN
- 2151-3740
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- 10.1080/21513732.2014.984334
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Abstract
International Journal of Biodiversity Science, Ecosystem Services & Management, 2015 Vol. 11, No. 2, 96–105, http://dx.doi.org/10.1080/21513732.2014.984334 Effects of management activities on vegetation diversity, dispersion pattern and stand structure of community-managed forest (Shorea robusta) in Nepal a,b c Bishwa Nath Oli and Mukti Ram Subedi * Department of Food and Resource Economics, Faculty of Science, University of Copenhagen, 25 Rolighedsvej, DK-1958 Frederiksberg b c C, Denmark; Department of Forests, Ministry of Forests and Soil Conservation, Kathmandu, Nepal; Department of Biological and Health Sciences, Texas A&M University-Kingsville, Kingsville, Texas, USA (Submitted 14 March 2014; accepted 2 November 2014; edited by Patricia Balvanera) Analyzing spatial patterns of population distribution in forests may assist to infer the underlying ecological processes and the factors responsible for pattern formation. This study aimed at analyzing the effects of management activities on species richness, diversity, distribution pattern, and forest stand structure in Chisapani Community Forest of Tanahun District, Nepal. The forest was stratified on the basis of crown cover and nested quadrat plots of 20 × 25 m were laid randomly. Trees having ≥5 cm diameter at breast height (dbh) were identified, and their diameter and height were recorded. Altogether, 44 −1 species were recorded representing 39 genera and 27 families. The mean species density of the forest was 192 trees ha and 2 −1 the average basal area was 16.2 m ha . Tukey’s post-hoc test showed the significant difference in species richness between open and dense crown class. Except Woodfordia fruticosa, all other species were found with patchy distribution. This study showed that unrestricted access does not necessarily maintain species diversity or regulate the forest stand structure, because people preferred species with high economic potential. Hence, a strategy for maintaining species diversity, regulating stand structure, and finding synergy between biodiversity conservation and conservation outcome is needed. Keywords: spatial distribution pattern; crown cover; species diversity; richness; community forestry Introduction found that global pattern analysis techniques (mostly analytic) were dominantly used in comparison with local In ecological discourse, determining spatial distribution techniques. However, global pattern does not necessarily patterns has drawn central attention (Condit et al. 2000). quantify spatial heterogeneity within a local scale. The A multitude of studies have contributed in understanding local spatial pattern analysis describes the variation of the role of spatial pattern in the assembly, association, and spatial pattern within the area of interest. Quadrat-based dynamics of vegetation that takes place in the ecosystem point pattern analysis, which is the area-based definition (e.g. Rohani et al. 1997; Perry et al. 2006; Martínez et al. of scale, is popular in ecological studies (e.g. Heltshe & 2010, 2013). The analysis of spatial distribution pattern Ritchey 1984; Olsen et al. 1996; Pélissier et al. 2001). assists to evaluate the contribution of factors responsible Scientists argue that understanding of the forest for the formation of this pattern. These factors may include dynamics is fundamental to develop sound management competition (Kubota & Hara 1995; Moeur 1997; Wolf systems (Fuhrer 2000; Sokpon & Biaou 2002; Obiri et al. 2005), establishment (Ledo et al. 2012), development 2002). Timely and accurate change detection of earth’s (Palik et al. 2003), mortality (Peet & Christensen 1987; surface features provides the foundation for better under- Das et al. 2008), and crown development (Stiell 1978). In standing the relationships and interactions between human a forest ecosystem, spatial distribution pattern may alter and natural phenomena to better manage and use resources the canopy light environment (Sprugel et al. 2009), as well (Lu et al. 2004; Deng et al. 2008). Researchers in the past as understory plant abundance, composition, and diversity. have used various methods for assessing forest conditions, Canopy density determines the air temperature and humid- depending upon individual preferences, research objective, ity in the understory (Sharpe 1996). The manipulation of and data availability (Gautam et al. 2004). Depending on crown cover through human activities (e.g. lopping) or the quality of data, remote sensing (RS) provides useful natural disturbance (e.g. wind throw) causes changes in spatial information to assess forest cover changes, but an light environment interaction and, in turn, changes the analysis of the social processes influencing land-use deci- structure and composition of species. sions is necessary to understand the factors leading to In nature, individuals of a population may be distrib- different conservation outcomes (Mascia et al. 2003). In uted in their habitat in a random, a clumped (aggregated), the recent days, climate change is attributed to change in or a regular (uniform) pattern. Perry et al. (2006) vegetation richness. Although there is limited support of mentioned two spatial (global and local) pattern analysis climate change in pattern formation, geographical techniques. Larson and Churchill (2012) in their review *Corresponding author. Email: mukti.subedi@students.tamuk.edu © 2015 Taylor & Francis International Journal of Biodiversity Science, Ecosystem Services & Management 97 information system (GIS) added vegetation analysis based larger spatial and temporal scale is beyond the scope of on the crown cover analysis may prove to be fundamental this study. However, the study based on cross-sectional in decision-making at management and activities level. use of data is expected to form the basis for such analysis Shorea robusta (generally known as Sal) forests are for future days. This study aims to (1) describe the rela- among the most disturbed forests in South Asia (Sapkota tionship between crown cover and stand structure of the et al. 2009), because of heavy pressure from local people species occurring in natural Sal forest under the hypothesis for timber, firewood, fodder, and litter collection. In Nepal, that spatial distribution pattern of woody species follows hill Sal forests are being handed over to local community the random pattern with respect to habitat and (2) examine for management as community forest (CF). Although the the effect of crown cover in species richness, diversity, and number and coverage of CF are increasing, there exists composition. limited information on biodiversity conservation in terms of species richness, taxonomic diversity, and crown cover- age due to lack of in-depth study and research (GoN Materials and methods 2009). This issue is highly aggravated due to choice of Study area major species selection by users. As community forest users groups (CFUGs) are managing such forests, appar- The study was carried out in hill Sal forest of Tanahun ently, this demands evaluation of stand structure, regen- district (see Figure 1). Tanahun district is situated in the eration condition, and temporal changes in species western development region of Nepal (27°03ʹ–28°05ʹ N diversity in order to assist in the formation of effective and 83°75ʹ–84°34ʹ E). The study area (171.29 ha) is management strategies without compromising fulfillment located between minimum and maximum of longitude of basic needs of local people. 27°58ʹ2″ and 27°58ʹ52″ N and latitude 84°19ʹ 53″–84° As per the provisions mentioned in operational plan 20ʹ 56″ E). The altitudinal range of the area varies from (OP), CFUG carry out tending operations; mostly thin- 435 to 694 masl. Average annual precipitation in the −1 ning, pruning, and shrub clearing. Ojha and Bhattarai nearest weather station in the district is 1691 mm year . (2001) documented that Sal is the single species highly The mean maximum and minimum temperatures are 29.5°C preferred even in the mixed Sal forest to convert their Sal and 17.4°C, respectively. mixed forest into pure Sal forest, exclusively written in the The area is characterized by the presence of secondary OP. This type of density management could result in and old growth Sal dominated forest following Adina changes in vegetation and species diversity. Therefore, cordifolia, Schima wallichii, Lagerstroemia parviflora, understanding the effect of such management activities and Mallotus philippinensis in tree layer. Most frequent on structure, diversity and richness, and local pattern is five species after Sal up to 535 masl, in decreasing order important for management purposes and at the policy level of frequency, are: S. wallichii, L. parviflora, A. cordifolia, as well, especially where there is no pragmatic policy like M. philippinensis, and Cleistocalys operculatus.Fourof in Nepal. Comparing effect of management intervention at them that are most frequent in lower altitude are same Figure 1. Location map of the study area. 98 B.N. Oli and M.R. Subedi except Semecarpus anacardium, which replace the C. crown cover measured at the interval of 5 m in each plot. operculatus in frequency in middle part of forest (535– We found all the plots laid in the respective crown class 635 masl). At the highest altitude region (>635) also S. agree with the ground based CD measurement using the wallichii is the most frequent associates followed by A. densiometer at 20 points in each plot. Spatial variability in cordifolia, L. parviflora, M. philippinensis, S. anacar- understory light is largely determined by several charac- dium. Selective logging, intense pressure of fuel wood teristics of overstory plants, for example vegetation struc- extraction, lopping, and top cutting of major species are ture, spatial pattern, height, and cover, which vary the causes of disturbance in the forest especially in low simultaneously along the grassland/forest continuum crown covered area. (Martens et al. 2000). In a forested ecosystem, tree crowns provide descriptive information in the evaluation of the condition of the forest (Niccolai et al. 2010). Crown cover Vegetation sampling (Baland et al. 2010) is known to be highly correlated with This study employed stratified random sampling based on other measures of the forest stock such as bole biomass, crown cover, and proportional allocation method was used total above ground biomass, and basal area (Tiwari & Singh 1987). The forest canopy is one of the chief deter- to determine the number of sample plots. Sample plots having dimension of 20 × 25 m, with three sub-plots of minants in assessing the plant growth and survival and the different sizes nested in the left corner of the biggest nature of the vegetation (Jennings et al. 1999). Hence, quadrat, were laid out for sampling purpose. Nested sam- crown cover can be used as the indicator of degradation pling plots were used to secure an adequate sampling of and/or disturbance of the forest. the different species studied (Christensen & Heilmann- Clausen 2009). Total 23 different plots were laid out in the forest. Each sample plots (20 × 25 m) was subjected to Data analysis the measurement of a tree (>29.9 cm dbh), dbh at 1.3 m above the ground level). Among three sub-plots, sub-plots In ecological study, species diversity (D) is a complex 2 2 size of 10 × 10 m (100 m ) and 5 × 5 m (25 m ) were used term because it takes into account both the species for the measurement of pole (10–29.9 cm dbh); and sap- richness (R) and evenness (E). In this study, richness ling (4–9.9 cm dbh), respectively. Moreover, all the regen- is the actual number of species used in data set based on erations of woody species in the sub-plot size of 10 m presence–absence data, whereas evenness represents the (2 × 5 m) were counted and recorded. All the species were effective number of species expressed as a proportion identified in-situ and any unidentified species were identi- of the actual number of species in the dataset (Tuomisto fied following Hara et al. (1978) and Press et al. (2000). 2013). The most widely used diversity measure is the Shannon-Wiener index (Shannon entropy) and the Gini Image analysis and crown cover classification Simpson index, but they are not themselves diversities Boundary delineation of the study area was completed (Jost 2006; Jost et al. 2010). Diversity is calculated with E-trex Vista H GPS; and so generated data were based on abundance data and is measured in effective made compatible to topographic digital data and orthopho- number of species (Hill 1973); to make the data set follow tos generated by the Survey Department of Nepal. the replication principle, we used Equation (1) to define The Geo-Eye image (multispectral and panchromatic the diversity of species band) of March 2009 (Path 98, Row 50) was purchased and re-projected to make compatible with topographic D ¼ sffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi (1) digital parameter. To achieve better visual interpretation, q1 q1 natural color composite was made based on multiband p p i i i¼1 pan-sharpened image produced on it. We could not per- form digital classification due to resource limitation. However, to come up with required degree of precision where D is a diversity of order q, p is the proportional and accuracy that can be obtained with digital image abundance of species i in the data set. Species diversity D processing (Desclée et al. 2006; Wang et al. 2008; (hereafter denoted as D) equals the inverse of mean p , and Niccolai et al. 2010), visual interpretation of forest status, it is the effective number of species. When q = 1, each condition, and composition were performed exploiting individual has the same probability of being chosen, and experience and knowledge of the field (Lu et al. 2004). hence the probability that the chosen individual represents For the purpose of this study, forest resource condition species i equals p . When q = 0, each species has the same was assessed in terms of crown cover following Land probability of being chosen irrespective of its proportional Resource Mapping Project (LRMP 1986) and the resulted abundance. When q = 2 basic sum (sum of the term inside crown density (CD) class were dense (>70% cover), thin the root) represent Simpson index (Simpson 1949;Hill (40–70% cover), and open (10–40% cover). To verify the 1973; Jost 2006) and hence equation is inverse of accuracy of visual image interpretation for crown cover, Simpson index, which represent the true diversity of we checked our resultant crown cover with the average order 2. International Journal of Biodiversity Science, Ecosystem Services & Management 99 Morisita’s index of dispersion (I )(Equation (3)) was pure Sal cover. To quantify the effect of associate tree used to discern the dispersion pattern of species (Krebs species on plant diversity and associated species produc- 1999). Uniform index value ðÞ M (Equation (4)) and tivity, we established the linear relationships for species aggregation index valueðÞ M (Equation (5)) were calcu- richness versus ABA/TBA ratio and D versus ABA/TBA lated as follows: ratio. Similarly, examining the effect of ABA/TBA ratio on plant diversity, regression equations were fitted for (1) "# P P 2 species richness versus canopy cover and (2) D versus x x I ¼ n (2) @ P P canopy cover. We used the regression equation due to the ðÞ x x nature of data (ratio) and to see the trade-offs between dependent and independent variables. x n þ x 0:975 M ¼ (3) ðÞ x 1 Socioeconomic and historical data collection and analysis Information about socioeconomic and demography along x n þ x 0:025 with the households’ knowledge on CF processes, historical M ¼ (4) ðÞ x 1 context of forest management, perception on forest condi- tion, energy use pattern, farm-tree growing, forest develop- where n is the sample size, x is the number of individuals, ment activities, forest products distribution and utilization, 2 2 x and x are the right tailed chi-squared value at 2.5% and rule enforcement were obtained from 30 randomly 0:025 0:975 and 97.5% with n − 1 degrees of freedom. Based on selected household surveys. Past historical information Equations (2–4) values of standard Morisita index I regarding the forest condition and underlying causes of forest structure change were collected through informal discussion were calculated following four different conditions; they are: with key informants during the field survey. In addition, two focused group discussion were conducted while understand- ð1Þ When I M >1; then @ c ing the historical dynamics of forest management and (5) associated socioeconomic drivers of forest condition change. I M @ c I ¼ 0:5 þ 0:5 Moreover, OP and constitution, of forest of different time, n M research reports related to study site, meeting minutes, policy, and legislative documents were also used to infer I 1 about socioeconomics related to forest dynamics. ð2Þ When M > I 1; then I ¼ 0:5 c @ p M 1 (6) Results Stand structure I 1 ð3Þ When 1> I > M ; then I ¼0:5 @ u p In total, 44 different species were recorded representing 39 M 1 genera and 27 families. Three canopy density class (here- (7) after referred as canopy class) that is dense, thin, and open and harbors 42, 18, and 8 species, respectively (Table 1). In all canopy class, Sal was largely dominant. In tree layers (>29.9 cm dbh), dominance of Sal was followed by A. ð4Þ When 1> M >I ; then u @ cordifolia, S. wallichii, and L. parviflora. The mean den- −1 (8) I 1 sity across all stratums was 192 trees ha . The highest I ¼0:5 þ 0:5 p −1 tree density was 180 trees ha for Sal, followed by S. M 1 −1 −1 wallichii (76 trees ha ), A. cordifolia (43 trees ha ), −1 L. parviflora (34 trees ha ), and M. philippinensis Value of I ranges from where negative value indicate uniform pattern, zero indicates a random pattern and posi- Table 1. Summary of forest structure across crown class. tive value indicates degree of aggregation (clumped) pattern. Diameter No. of Basal Additionally, following Jobidon et al. (2004), we also Species stem area −1 2 −1 calculated total basal area (TBA) of species at plot level Crown class richness (ha ) (m ha ) Mean CV (%) and basal area of major associated species of Sal (ABA). Open (0–40%) 8 100 10.99 33.2 54.85 ABA to TBA ratio at plot level is used to represent the Thin (40–70%) 18 164 12.94 27.9 54.54 proportion of Sal associated species. A value of proportion Dense (>70%) 42 213 17.95 29.5 48.46 (1:0) represents pure associates’ species cover, while the Total 44 192 16.18 29.3 49.84 reverse proportion (0:1) that leads to value 1 represent the 100 B.N. Oli and M.R. Subedi −1 (32 trees ha ). As expected, highest stem density was philippinensis, and S. robusta were found in all three CD recorded for dense, followed by thin and open CD cate- class, while rest of the five species were found only in two gory (see Table 1). The average basal area across all stratums as shown in Table 2. 2 −1 stratums was 16.2 m ha . The highest average was Distribution pattern of species like P. emblica, T. 2 −1 recorded for dense stratum (i.e. 18 m ha ), while the tomentosa, and S. anacardium was not consistent across 2 −1 least was recorded for open CD (i.e. 11 m ha ). The CD class (Table 2). highest average diameter (33.2 cm) was recorded for open crown class, while the least was recorded for thin crown class (27.9 cm). Number of individuals is varied from 3 to Canopy density and its effects on plant species richness, 16 per quadrat. diversity, and abundance Significant inverse relationship was found while plotting True diversity (q = 2, Equation (2)) varies from 0.398 to the total number of individuals per hectare against diameter 2.59 in Chisapani CF. Species diversity was highest in the class (Figure 2(a)) for whole forest (R =0.967, p =0.011) adj dense crown class followed by thin and open. Distance and open crown class (Figure 2(b)). Similarly logistic from nearest settlement significantly predicted diversity, equation was found significant for the thin (Figure 2(c)) β = 0.639, t(21) = 3.810, p < 0.001. Distance from nearest and dense crown class (Figure 2(d)). settlement also explained a significant proportion of var- In open crown category fewer number of larger trees 2 iance in diversity, R = 0.409, F(1,21) = 14.517, p < 0.001. exist and the rate of number of individuals fall with Similarly, distance from nearest road varies significantly increase in diameter class which is greater for denser with species diversity, β = 0.721, t(21) = 4.744, p < 0.001. crown category than for thin crown category (Figure 2(d)). Distance from nearest settlement also explained a significant proportion of variance in diversity, R = 0.520, F(1,21) = 22.792, p < 0.001. The highest Spatial distribution pattern species diversity was recorded in South, Southeast, and Of the 18 species, eight species were recorded only in West facing. However, the analysis of variances does not dense crown canopy. They are: Albizia procera, C. oper- show significant changes in diversity with slope culatus, W. fruticosa, Syzigium cumini, Castanopsis (F = 0.388, p = 0.684). Similarly, species diversity does indica, Swida oblonga, Wendlandia exserta, and not vary significantly across the crown class (F = 1.902, Colebrookea oppositifolia. Wightia speciossissima, p = 0.177). On the contrary, species richness across crown Terminilia tomentosa, L. parviflora, and Phyllanthus class was significant only at the 10% chance of commit- emblica follow either random or aggregated pattern. ting type I error (F = 3.387, p = 0.059). Tukey’s post-hoc Only one species, W. fruticosa was found uniformly dis- test shows the difference between open and dense crown tributed, whereas the rest of all other species were found class; dense crown class had higher species richness than with patchy (clumped) distribution. L. parviflora, M. open crown class. Figure 2. Relationship between number of individuals per hectare to mid value of diameter class for (a) whole forest and (b) open, (c) thin, and (d) dense crown density category. International Journal of Biodiversity Science, Ecosystem Services & Management 101 −1 Table 2. Distribution pattern and density (number ha )of Discussion species across crown class. The study revealed that the number of stems per hectare and basal area per hectare did not vary significantly across Crown density the three CD. The tree layer had the lowest stem density, progressively increases with saplings and seedlings, and Species Open Thin Dense revealed the phenomenon that is generally exhibited by a R C Phyllanthus emblica 20 73 healthy vegetation community (Mligo et al. 2009). The C R Terminalia tomentosa 47 30 study showed the direct relation between density of woody C C Wightia speciosissima 20 33 R C species and the CD. This can be attributed to decreased Semecarpus anacardium 20 32 R R C human pressure with increase in CD, as the dense forest is Lagerstroemia parviflora 40 33 33 C C Gracinia xanthochymus 60 71 located relatively far from the nearby settlement. C C Schima Wallichii 80 76 Moreover, higher diameter class had lower density across Woodfordia fruticosa 20 the CD class (Figure 2). Although the local people gen- Colebrookea oppositifolia 35 erally concentrate on lower diameter class and especially Syzizium cumini 100 on thin crown class, still the density of small-sized tree is Castonopsis indica 100 Cleistocalyx operculatus 47 higher in the forest. In Chisapani CF, density of trees is Swida oblonga 69 progressively declined from lower to higher diameter Albizia procera 53 class, as revealed by inverse relationship (Figure 2(a)). Wendlandia exserta 35 C C This observation is in line with the observation of Adina cordifolia 47 28 C C C Sapkota et al. (2009) in seasonally dry deciduous Sal Shorea robusta 470 700 389 C C C Mallotus philippinensis 260 127 80 forest in Terai area of Nepal. They found an inverse relationship between the overall stand density and the Note: The superscripts R, C, and U, respectively, indicate random, diameter class in all forests, except in the most disturbed clumped, and uniform distribution pattern. forest. Our results of mean basal area of trees per hectare was higher than that of Sagar et al. (2003) (8.5– 2 −1 Species richness of the three combined strata (CD) was 13.8 m ha ) in the dry tropical forest of India and 2 −1 only moderately affected by the proportion of associated Timilsina et al. (2007) (13.4 m ha ) in western Terai of species of Sal in the canopy (R = 0.321, p = 0.004) (see Nepal. Similar results were recorded by Sapkota et al. adj 2 −1 Table 3 and Figure 3(a)). Species diversity reached to peak (2009) (12.5–19.3 m ha ) along the disturbance gradient (at ABA/TBA = 0.7), started to increase at 0.1 and in Chure area of Nepal. declined after 0.7, and the relation was quadratic. Likewise, observation of relatively low stem density −1 Species diversity and richness are linearly declined as (192 trees ha ) is consistent with other studies (e.g. the ratio of ABA to TBA increased. Any significant dif- Rautiainen 1999; Sagar et al. 2003). However, densities ference between the abundance of species (all), and regen- of Sal forests in Bardia National Park of Nepal reported by −1 eration across CD was not found. However, the study Shrestha and Jha (1997) (348 trees ha ), in Tanahun −1 district of Nepal by Rai et al. (1999) (658 trees ha and revealed the significant difference between tree species −1 743 trees ha ), and in India (Shukla & Pandey 2000) abundance across CD (F = 7.631, p = 0.004). As expected, −1 (814 trees ha ) (Rawat & Bhainsora 1999) (254– numbers of tree species were found increased with −1 376 trees ha ) superseded the overall mean. increase in CD, nevertheless, thin and dense CD does Human intervention on forest for satisfying their needs not show any difference. of fuelwood, fodder, litter, and minor forest products, as Regression on diversity versus canopy class did not well as grazing and browsing can alter species’ habitats show any significant relation (see Table 3). This signifies (Pandey & Shukla 2001). Consequently, species richness that although the species richness increases with increase and diversity in disturbance prevailing area largely depend in CD, it does not necessarily increase the species diver- on the species response to such disturbances; some may sity because the species diversity is function of both species Richness and species abundance. withstand the disturbances, while others may become Table 3. Regression equation for the relation between species richness (R) and ratio of Sal associates’ basal area to total basal area (ABA/TBA); true diversity (D) and ABA/TBA; R and crown density class (CD), and D and CD. Model P name Model form β β β R value Figure 0 1 2 adj Linear R = β +(β × ABA/TBA) 6.576 (0.000) 5.656 (0.004) 0.321 0.004 3a 0 1 Quadratic D = β +(β × ABA/TBA) + (β × ABA/TBA ) 1.083 (0.000) 3.053 (0.004) −2.179 (0.066) 0.519 0.000 3b 0 1 2 Exponential ln(R) = ln(β )+(β × CD) 3.988 (0.007) 0.999 (0.064) 0.119 0.064 3c 0 1 Linear D = β +(β × CD) 0.845 (0.103) 1.077 (0.174) 0.045 0.174 Not shown 0 1 Note: Figure in the parentheses indicate p value of the regression coefficients. 102 B.N. Oli and M.R. Subedi Figure 3. Relationship between (a) species richness (R) and the ratio of Sal associates basal area to total basal area (ABA/TBA), (b) species diversity and ABA/TBA, and (c) R versus crown cover. extinct locally (Sagar et al. 2003; Mligo et al. 2009). True 1973). Therefore, disturbance in the dry deciduous forest species diversity of Chisapani CF is low; ranges from can potentially lead to a decrease in stability and com- 0.398 to 2.593 and average species diversity per plot is plexity of the ecosystems. Researchers indicated that 1.519. This observation is in line with Stainton (1972) shifting of clumped to uniform distribution pattern is explaining species–poor nature of Sal forest. Average associated with change from higher to lower stem density diversity of species increases with increase in CD class. (Sagar et al. 2003; Sapkota et al. 2009), and the result of Open crown class has almost half less diversity than dense this study is in line with their findings. Distribution category. This may be due to either proportional allocation patterns of P. emblica, T. tomentosa, S. anacardium of sampling plots according to species-area relationships; were not consistent across CD class, indicating that spe- larger area harbors, more species or selective logging cies response varies across crown openings which create carried out in the previous year’s leading to loss of the different habitat condition through variation in light. regeneration of species. Similarly, in case of T. tomentosa changes in distribution Shrestha and Jha (1997) mentioned that selective pattern (thin to dense, CD) support the hypotheses that logging, burning, overgrazing, and indiscriminate cutting the random pattern in fact is transformation of clumped for firewood and building timbers can turn old growth patterncausedbydisturbancesand competitionofneigh- Sal forests into heavy admixtures of other tree species, boring trees (Lepš & Kindlmann 1987; Rozas & Antonio especially T. Tomentosa. The result of this study also Fernandez prieto 2000). The study revealed that such supports this phenomena; reduction of density of species shift in pattern from one CD to another hinted that from thin to dense crown category. This also proves that crown cover can be considered as disturbance gradient. the CD class can be considered as disturbance gradient. Out of 18 species in Table 2 one species has random To put it different, in the present study species diversity distribution in open, three in thin, and one in dense is increased with decreasing level of disturbance. Leigh crown category, which reject our hypothesis that the (1965) suggested that stability increases with the com- spatial distribution pattern of woody species follow the plexity of the ecosystems that is with the number of random pattern with respect to habitat. One possibility, in species and with the number of interactions between this case, in shift in distribution pattern may be due to them. MacArthur (1965) pointed out that diversity is a light-loving character of species, which was not found in function of the number of species. The stability has been case of dense top canopy. On the other hand, decrease in reported to increase with diversity (Shafi & Yarranton density was found in shade-loving species like Mallotus International Journal of Biodiversity Science, Ecosystem Services & Management 103 philipinensis with increase in CD. Nevertheless, com- forests’ productivity by means of thinning and pruning, pounded effects of anthropogenic and natural distur- without affecting local needs are required. Nevertheless, bances affect species’ distribution patterns (Rozas & study to quantify for thresholds (standard) should be Antonio Fernandez prieto 2000;Kiester 2013). In the carried out at community-managed Sal forest for species present study, species represented by single individuals diversity to be reached within the canopy cover of varied from 25% (open crown) to 38% (thin crown). This mixed-Sal forest. is higher than the observation of Sagar et al. (2003)(18– 30%). Regardless of disturbance (crown category), Sal Acknowledgments was found in higher density being dominant species of the forest. Therefore, Sal can be considered as distur- We extend our thanks to local inhabitants of Chisapani CFUG especially those who were involved in forest inventory. Officials bance tolerant species (Pandey & Shukla 2001). at District Forest Office also deserve our sincere thanks for their Increasing the proportion in basal area of associate tireless support in logistics and forest inventory. We are also species of Sal in the Chisapani CF showed a positive thankful to Mr Rabindra Maharjan for his support in RS and linear relation with species richness (Figure 3(a))and GIS works. Jenni Vinson deserves sincere thanks for her support curvilinear to species diversity (Figure 3(a)). Species in English correction. We thank two anonymous reviewers and editors for their comments in the early version of manuscript. diversity increased till the ABA/TBA ratio reached 0.7, after which it started to fall (Figure 3(b)). Experiencing frequent disturbances, natural mixed Sal forest maintains Funding higher levels of diversity in comparison to close canopy We would like to thank DANIDA-funded ComForM project forest. However, the results suggest that denser canopy [grant number 10-015 LIFE] for providing financial support to coverage shows higher species richness (Figure 3(c)) this study. and diversity (figure not shown). 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Journal
International Journal of Biodiversity Science, Ecosystem Services & Management – Taylor & Francis
Published: Apr 3, 2015
Keywords: spatial distribution pattern; crown cover; species diversity; richness; community forestry