Tropical Ecology 56(3): 275-288, 2015 ISSN 0564-3295 © International Society for Tropical Ecology www.tropecol.com Analysis of fragmentation and disturbance regimes in south Gujarat forests, India 1 1* 1 2 3 3 G. D. BHATT , S. P. S. KUSHWAHA , S. NANDY , KIRAN BARGALI , P. S. NAGAR & D. M. TADVI 1Forestry and Ecology Department, Indian Institute of Remote Sensing, ISRO, Dehradun 248001, Uttarakhand, India 2Department of Botany, Kumaun University, Nainital 263001, Uttarakhand, India 3 Department of Botany, M.S. University of Baroda, Vadodara 391110, Gujarat, India Abstract: Forests, world over, have degraded, fragmented, and depleted as human population has swelled. In the present study, the forest fragmentation and the disturbance regimes were assessed in south Gujarat using satellite image-based forest and land use mapping followed by landscape analysis using Spatial Landscape Modelling (SPLAM) software. The on-screen visual interpretation of Resourcesat-1 LISS-III imagery facilitated in mapping of 9 forest and 12 non-forest classes. The observations revealed that 51.68 % of the forest area had low fragmentation while the rest had medium to high fragmentation. Among the vegetation types, 62.84 % of Tropical Moist Mixed Deciduous (TMMD) and 54.88 % of Tropical Mixed Dry Deciduous (TMDD) forests had low level of fragmentation whereas 15.5 % mangrove forest had high fragmentation. The study also showed that 72.53 % of the total forest area had low disturbance. High disturbance was noticed in Riverine forest (22.78 %) while TMMD forest was found to be less disturbed than TMDD forest. District-wise analysis revealed that forests of Valsad, Navsari and Bharuch were highly disturbed as well as fragmented whereas forests of The Dangs, Surat and Narmada had low disturbance and fragmentation. The study demonstrated important role of remote sensing, GIS, and SPLAM in forest/land use mapping and disturbance regimes and fragmentation status assessment. Resumen: Los bosques del mundo entero se han degradado, fragmentado y empobrecido conforme la población humana ha aumentado. En el presente estudio se evaluó la fragmentación de los bosques y los regímenes de disturbio en el sur de Guyarat mediante la cartografíade los bosques y el uso de la tierra basado en imágenes de satélite, seguido de análisis del paisaje usando el programa Spatial Landscape Modelling (SPLAM). La interpretación visual en pantalla de las imágenes Resourcesat-1 LISS-III facilitó en la cartografía de 9 clases de bosque y 12 clases no forestales. Las observaciones mostraron que 51.68 % de la superficie forestal estaba poco fragmentada, mientras que la fragmentación en el resto varió entremedia y alta. Entre los tipos de vegetación, 62.84 % del bosquetropical húmedo caducifolio mixto (TMMD) y 54.88 % del bosque tropical mixto seco deciduo (TMDD) tenían un nivel bajo de fragmentación, mientras que en 15.5 % del manglar la fragmentación fuealta. El estudio también mostró que 72.53 % de la superficie forestal estaba poco perturbada. Se registró perturbación alta en el bosque ribereño (22.78 %), mientras que se encontró que el bosque TMMD estaba menosperturbado que el bosque TMDD. Un análisis por distritos reveló que los bosques de Valsad, Navsari y Bharuchestaban fuertemente perturbados y fragmentados, mientras que los bosques de The Dangs, Surat y Narmadateníanniveles bajosde perturbación y fragmentación. El estudio demostró el importante papel de la percepción remota, los SIG y el programa SPLAM para la cartografía del uso forestal y de la tierra, así comoen la evaluación de los regímenes de *Corresponding Author; e-mail: [email protected] 276 ANALYSIS OF FRAGMENTATION AND DISTURBANCE REGIMES disturbio y el estado de fragmentación. Resumo: Por todo o mundoas florestas têm-se degradado, fragmentado e empobrecido com o aumento da da população humana. No presente estudo, a fragmentação florestal e os regimes de perturbação foram avaliados no sul de Gujarat usando como base imagens de satélite da floresta e o mapeamento do uso do solo, seguido de análise da paisagem com recurso ao software de Modelação Espacial da Paisagem (SPLAM). A interpretação visual no monitor da imagemda floresta usando o Resourcesat-1 LISS-III facilitou o mapeamento de 9 classes de floresta e 12 classes não-florestais. As observações mostraram que 51,68 % da área de floresta apresentava baixa fragmentação, enquanto o restantorevelou uma fragmentação média a alta. Entre os tipos de vegetação, 62,84 % da floresta Tropical Mista Húmida Decídua (TMMD) e 54,88 % da floresta Tropical Mista Seca Decídua (TMDD) apresentavam baixo nível de fragmentação, enquanto que 15,5 % do mangal apresentava alta fragmentação. O estudo também mostrou que 72,53 % da área total de floresta foi sugeita a baixa perturbação. Alta perturbação foi notado naFloresta Ribeirinha (22,78 %), enquanto a floresta TMMD revelou ter sido menos perturbada que a TMDD. A análise por Distrito mostrou que as florestas de Valsad, Navsari e Bharuch foram altamente perturbadas, assim como fragmentadas, enquanto que as florestas de The Dangs, Surat e Narmada apresentavam baixa perturbação e fragmentação. O estudo demonstrou o papel importante dos sistemas de detecção remota GIS e SPLAM, no mapeamento da floresta / uso da terra e dos regimes de perturbação e avaliação do estado de fragmentação. Key words: GIS, landscape, land use, remote sensing, SPLAM, vegetation type. Introduction involving landscape level assessment of the disturbance regimes and the forest fragmentation Forests in India have been used by the people is known from this part of India. over millennia for a variety of purposes and The geospatial technology, including remote practices (Lele & Hegde 1997; Uma Shankar et al. sensing, geographic information system (GIS) and 1998). Of these, the livestock grazing, non-timber global positioning system (GPS), involving acqui- forest product, fodder, medicine, food, timber, sition and analysis of the remote sensing data to resin, dye, fuel, oil, tannin, and other forest extract meaningful information, has developed products collection are historic and continuing substantially in the past four decades (Mas 1999). uses of the forest (Banerjee 1995; Bhat et al. 2001; Remotely-sensed data has been used in the past FAO 2006). Among various causes of forest for a variety of purposes such as forest cover fragmentation and degradation, the live-stock monitoring (NRSA 1983), land use / land cover grazing, fuelwood, fodder extraction, and burning mapping and monitoring (Kushwaha 1990; Kumar for cultivation are recognized as the chronic & Mathur 2014) stand volume assessment (Köhl & disturbances (Singh 1998) with substantial impact Kushwaha 1994), biomass estimation (Pandey et on flora, fauna, soil, water and the micro-climate al. 2010; Roy & Ravan 1996), wildlife habitat (Tilman & Lehman 2001). The extraction, evaluation (Kushwaha & Roy 2002; Nandy et al. exceeding regeneration, depletes forest ecosystems. 2012; Singh & Kushwaha 2011), etc. An effort was The pressure on forests has steadily increased made in late nineties to use remote sensing data with an ever-increasing human population in the for nationwide rapid biodiversity characterization country. The quantitative studies on the landscape and a three-pronged method involving satellite level impacts of disturbance on the forests in India imagery, landscape analysis and field inventory of are relatively few (Shahabuddin & Prasad 2004). biodiversity was developed for the first time in Majority of the studies have focused on the India and implemented (Roy & Tomar 2000). impacts either on vegetation (Kumar & Shaha- Several studies have subsequently used the metho- buddin 2005; Madhusudan 1999; Sagar et al. 2003; dology to characterize biological richness in the Uma Shankar et al. 1998), soil (Sahani & Behera country (Kushwaha et al. 2005; Nandy & 2001), or wildlife (Madhusudan 2000). No study Kushwaha 2010). BHATT et al. 277 Forests in India are subjected to various Gulf of Khambhat. The south Gujarat (21°14'- disturbance regimes and majority of them are 22°49' N and 72° 22' - 74°15' E) consists of seven anthropogenic. Disturbance, a common and wide- districts viz., Valsad, Navsari, The Dangs, Surat, spread phenomenon in our anthropocentric world, Bharuch, Narmada, and Vadodara, covering a is defined as a discrete event with the passage of geographical area of 31,495 km2 (Fig. 1). The time that modifies landscapes, ecosystems, commu- plains of south Gujarat are watered by Purna, Par, nities and the populations (Forman & Godron Damanganga, Auranga, Kolak, Ambica, Darota, 1986). The disturbance also leads to processes like Narmada, and Tapi rivers. The region shows a fragmentation, degradation, depletion, species typical sub-humid to humid climate (Anonymous migration, and extinction. The impact of the 2006). The mean annual temperature is about 26 disturbance regimes on the landscapes can be well °C and the mean summer and winter tempe- understood by analyzing the spatial and temporal ratures are 41 and 22 °C respectively with 70 - 75 % nature of the disturbance (White & Pickett 1985). mean relative humidity. The average annual At landscape level, disturbance is related to patch rainfall varies from 1300 - 2200 mm (Patel 1997). structure and spatial arrangement of patches, and The major forest types in the south Gujarat determines the fate of patches, their size, and the are: Moist Teak Forest (3B/C1(b,c)), Southern Moist duration. Severe disturbance generally has depre- Mixed Deciduous Forest