Forest Land-use change in Ngoc Phai commune, Cho Don district, Bac Kan province, Vietnam (1990-2005)

Đàm Việt Bắc và cs Tạp chí KHOA HỌC & CÔNG NGHỆ 77(01): 97 - 102 97 FOREST LAND-USE CHANGE IN NGOC PHAI COMMUNE, CHO DON DISTRICT, BAC KAN PROVINCE, VIETNAM (1990-2005) Dam Viet Bac, Dam Xuan Van * College of Agriculture and Forestry - Thai Nguyen University SUMMARY The study was conducted at the Ngoc Phai Commune, Cho Don District, Bac Kan Province, Vietnam. The aimed to determine land-use changes (LUCs) for the last 15 years (1990-2005) of Doi Moi (renovation) ra in the mountainous region of northern Vietnam. For spatial data, the Geographic Information System (GIS) was applied as a tool for determining LUCs. Three land-use maps (1990, 1998 and 2005) were overlaid and grouped into two intervals (1990-1998 and 1998- 2005). Several thematic maps were created such as slope, elevation, drainage and road maps. Moreover, the study site was divided into 204-grid cells with 500 m x 500 m/cell or 25 ha/cell to identify and quantity the area and location of the land-use changes associated with the grid cell level. For the period 1990-1998, the total area of forest degradation was 109.31 ha. This occurred at 15°-35° slope, 500-700 masl and at a distance of 500-1000m from location of LUCs to the main road. Forest restoration for the same time period was 108.30 ha mainly at 15°-35° slope, 400-700 mal and at a distance of 100-250 m followed by 250-500 m and 500-750 m. For the period 1998- 2005, forest degradation had a total area of 625.47 ha mainly at 15°-35°slope, 400-600 masl and at a distance of 250-500 m followed by 500-750 m and 750 – 1000 m. Forest restoration for the same time period was 657.94 ha mainly at 15°-35° slope, 400-700 mal and at a distance of 250-500 m followed by 500-750 m and 750-1000 m. Keywords: Land use change, mountainous region, northern Vietnam INTRODUCTION * Three-quarters of Vietnam‟s total land area of 33.104 million hectares is occupied by hills and mountains. The remaining one-third is home to the national population which have undergone rapid changes following socio- economic developments. Forest and land, the main sources of local production system, has been impacted severely over the last decades. Researches on land-use and land-use planning have been carried out in Northern Vietnam but have not fully looked into the driving forces of land-use change as influenced by renovation policies. For this reason, research in this area was conducted. The study attempted to review the biophysical and socio-economic conditions, estimate land-use change across three-time periods by using Geographic Information System (GIS), identify the driving forces of land-use change both at the local and exogenous levels and create GIS database. Results of the study would contribute to policymakers in creating * Tel: 0982166696; Email: damxuanvan@yahoo.com guidelines relevant to forestry and rural development sectors. MATERIALS AND METHODS GIS Processing for Analysis of Land-Use Changes For spatial data, existing digital GIS files of land-use maps (1990, 1998, and 2005) from SAM Project and Natural and Environmental Office of Bac Kan province were used. This was combined with ground verification generated during the time of data gathering by intersecting land-use themes 1990-1998, and 1998–2005. Aside from these, topographical, drainage and slope maps were interpreted in Philippines and intersected with several thematic maps by ArcGIS 9.0. Finally, grid cell level (25 ha/cell) for the study site was made. For temporal data, all the attribute tables on Arcview GIS 3.2a and AcrGIS 9.0 were exported to dBase IV files of Excel program, and then to SPSS 12.0 for statistical analysis of output tables. Means, frequencies, ranges, percentages land-use change matrices and charts were used to compare the data of land- Số hóa bởi Trung tâm Học liệu - Đại học Thái Nguyên Đàm Việt Bắc và cs Tạp chí KHOA HỌC & CÔNG NGHỆ 77(01): 97 – 102 98 use change areas of eight forest and land-use types; (dense forest, open forest, shrubs, upland crops, grasslands, mosaic and other lands). Descriptive statistics was used to analyze data on biophysical and socio-economic conditions of the study site. The results were presented as percentages, averages or means, ranges and graphs, where applicable. RESULTS AND DISCUSSION Determinants of Land-Use Changes The change in land-use was determined by overlaying land-use maps of 1990-1998, and 1998-2005. Overlaid maps was done in ArcView GIS 3.2a and AcrGIS 9.0. The results of overlaid maps are shown in Figure 1 and Figure 2. Dynamics of Land-Use Changes The land-use changes in Ngoc Phai for the past eight-year period are shown in Table 1. The data indicates that forestland and shrub areas have small reduction in the area of dense forest. It accounted for –191.02 ha or a -14.58% drop while there was a steady rise between 1990 and 1998, +395 ha or 73.84%. In the open forest and shrublands, There was a reduction of –87.18 ha or -7.52%. There was a marked increase in the area of paddy field with +40 ha or 29.95%. In upland crops, a reduction was also observed, –139 ha or - 34.50%. A decline of –21 ha or -10.34% in grasslands was also noted. Between 1998-2005, a high rate of forest disturbance occurred in the dense forest; the forest decreased by –103.21 ha or -9.22%, followed by shrubs with -110.91 ha or - 10.34%. The open forest declined by –2.51 ha or -0.27% and the mosaic lands by –3.32 ha or -0.29%. For the other kinds of land- uses, sharp increases were observed. In the upland crops, an increase of +110.88 ha or 41.78 and in paddy field with 62.76 ha or +36.10%. Moreover, a rise of +29 ha or +41.89% in other lands and +16.62 ha or +9.22 % in the grasslands was also realized. Overall, the rate of forest disturbance in the period of 1990-1998 were as follows: dense forest declined by -23.87 ha or -1.82% annually and shrublands by –10.89 ha or - 0.94% annually. During 1998-2005 period, forest degradation was down to –14.74 ha or -1.32% annually in the dense forest, and - 15.84 ha or -1.47% annually in the shrublands. However, there was an increase in the open forest during first period of +9.23 ha or +0.31% annually (Table 1). Figure 1. Land-use change map, 1990-1998 Figure 2. Land-use change map, 1998-2005 Số hóa bởi Trung tâm Học liệu - Đại học Thái Nguyên Đàm Việt Bắc và cs Tạp chí KHOA HỌC & CÔNG NGHỆ 77(01): 97 - 102 99 Table 1. Land-use changes across three-time periods TYPES OF LAND-USE 1990 1998 2005 CHANGE IN 1990-1998 CHANGE IN 1998-2005 (ha) (ha) (ha) (ha) % (ha) % Dense Forest 1310.14 1119.12 1015.91 -191.02 -14.58 -103.21 -9.22 Open Forest 535.97 931.71 929.20 +395.74 +73.84 -2.51 -0.27 Shrubs 1159.52 1072.34 961.43 -87.18 -7.52 -110.91 -10.34 Paddy Field 133.8 173.87 236.63 +40.07 +29.95 +62.76 +36.10 Upland Crops 405.15 265.37 376.25 -139.78 -34.50 +110.88 +41.78 Grasslands 201.3 180.30 196.92 -21.00 -10.43 +16.62 +9.22 Mosaic 369.86 359.86 356.54 -10.00 -2.70 -3.32 -0.92 Other Lands 57.72 70.88 100.57 +13.16 +22.80 +29.69 +41.89 *Figures preceed with + sign indicates an increase; - sign indicates a decrease Table 2. Transition matrix of land-use change for 1990 – 1998 1990 1998 1990 TOTAL Dense Forest Open Forest Shrubs Paddy Field Upland Crops Grass Land Mosaic Other Land Dense Forest 1110.83 199.31 1310.14 Open Forest 8.29 527.69 535.97 Shrubs 100.01 1059.51 1159.52 Paddy Field 133.80 133.80 Upland Crops 99.71 40.08 265.37 405.15 Grass Land 5.00 180.29 16.00 201.30 Mosaic 359.86 10.00 369.86 Other Lands 12.83 44.89 57.72 1998 TOTAL 1119.12 931.71 1072.34 173.87 265.37 180.29 359.86 70.89 4173.45 Change in (ha) -191.02 +395.74 -87.18 +40.08 -139.79 -21.00 -10.00 +13.17 Change in (%) -14.58 +73.84 -7.52 +29.95 -34.50 -10.43 -2.70 +22.82 Process of Land-Use Transitions Period 1990-1998 (During Forest Land Allocation Program). Table 2 shows the transition matrix where 199.31 ha or 15.21% of the total of dense forest are was converted to open forest; a slight conversion in open forest to dense forest (8.29 ha or 1.55%). For shrubs, 100.01 ha were converted to open forest and 1059.51 ha or 91.37% remained unchanged. The rate of land-use change between 1990- 1998 (Table 2) shows that there was no conversion to paddy fields during 1990-1998. Paddy field remained its original area of 133.80 ha. A total of 40.08 ha (3.83%) of upland crops was converted to paddy field and 99.71 ha (24.61%) to open forest. A small area of grassland, 5.00 ha (2.48%) was converted to open forest and 16.00 ha (7.95%) to other lands. Period 1998-2005 (After Forest Land Allocation Program). The transition matrix (Table 3) shows the land-use change over a period of seven years. The dense forest area was transformed into shrubs area by 290.25 ha or 25.94% of total dense forest land. Other lands increased by 61.79 ha or 5.52 %, grasslands by 16.68 ha or 1.49%, paddy fields by 7.16 ha or 0.64% and mosaic lands by 0.46 ha or 0.04%. The high rate of forest disturbance was from conversion of 124.52 ha open forest (13.36%) into shrubs, conversion of 169.24 ha of open forest (18.16%) into dense forest, 106.39 ha of open forest Số hóa bởi Trung tâm Học liệu - Đại học Thái Nguyên Đàm Việt Bắc và cs Tạp chí KHOA HỌC & CÔNG NGHỆ 77(01): 97 – 102 100 (11.42%) into upland crops, 11.34 ha of open forest (1.22%) into paddy fields. The other converted areas of open forestland were less than 1%. There was a dramatic reduction shrublands. Only 381.39 ha or 35.57% devoted to shrubs remained its original area, with 415.86 or 38.37% of shrublands converted to open forest land, with 156.84 ha or 14.63% of shrublands converted to grasslands, 72.81 ha or 6.78 % shrublands changed to dense forest and 33.15 ha or 3.09% of shrublands diverted to paddy fields. There were no change to both the paddy field and upland crops. Paddy fields remained at173.87 ha and upland crops remained at 265.37 ha or 100% of their original lands. Grasslands were reduced drastically to 14.10 ha or 7.82%, with 130.87 ha or 72.58% of grasslands transformed into shrublands, 20.80 ha of grasslands (11.54%) changed to dense forest, 9.27 ha or 5.14% of grasslands changed into other land-use category, and 3.61 ha or 2.00% of grasslands changed to upland crops (Table 3). Table 3. Transition matrix of land-use change, 1998–2005 1998 2005 1998 TOTAL Dense Forest Open Forest Shrubs Paddy Field Upland Crops Grass Land Mosaic Other Land Dense Forest 742.77 290.25 7.16 16.68 0.46 61.79 1119.12 Open Forest 169.24 513.34 124.52 11.34 106.39 4.30 2.56 0.02 931.71 Shrubs 72.81 415.86 381.39 33.15 0.68 156.84 10.91 0.69 1072.34 Paddy Field 173.87 173.87 Upland Crops 265.37 265.37 Grass Land 20.8 130.87 1.43 3.61 14.10 0.22 9.27 180.3 Mosaic 13.98 5.68 0.81 332.7 6.69 359.86 Other Lands 10.29 20.42 4.00 0.20 4.19 9.69 22.10 70.88 2005 TOTAL 1015.91 929.20 961.43 236.63 376.25 196.92 356.54 100.56 4173.45 Change in (ha) -103.21 -2.51 -110.91 +62.76 +110.88 16.62 -3.32 29.68 Change in (%) -9.22 -0.27 -10.34 +36.10 +41.78 9.22 -0.92 41.87 Net Changes Detected by Post- Classification Method Table 4. Land-use change by post-classification method NATURE OF CHANGE AREA CHANGE IN 1990-1998 AREA CHANGE IN 1998-2005 (ha) (ha) Loss of forest 199.31 625.47 Gain of forest 108.30 657.94 Based on the post-classification method of land-use change in two periods during and after implementation of the land allocation program, 12 important land- use changes were found consistent in both sub-periods. The results further showed that the forest disturbance was 199.31 ha in the first period and in the second period, 625.47 ha. Forest increased 108.30 ha and 657.94 ha in the first and second periods, respectively (Table 4). The original area of the dense forest class and the open forest class, 84.79% and 98.45% of respectively did not change in the first period (1990-1998). Likewise, in the second period (1998-2005), 66.37% and 55.10% of the dense forest and the open forest did not change, respectively (Table 5). Số hóa bởi Trung tâm Học liệu - Đại học Thái Nguyên Đàm Việt Bắc và cs Tạp chí KHOA HỌC & CÔNG NGHỆ 77(01): 97 - 102 101 Table 5. Land-use areas which did not change LAND-USE TYPE AREA IN 1990- 1998 PERCENT OF 1990 TOTAL AREA IN 1998- 2005 PERCENT OF 1998 TOTAL (ha) (%) (ha) (%) Dense Forest 1110.83 84.79 742.77 66.37 Open Forest 527.69 98.45 513.34 55.10 Shrubs 1059.51 91.37 381.39 35.57 Paddy Field 133.80 100.00 173.87 100.00 Upland Crops 265.37 65.50 265.37 7.82 Grass Land 180.29 89.56 14.10 92.45 Mosaic 359.86 97.30 332.70 22.10 Other Lands 44.89 77.77 22.10 31.18 Total 3682.24 2445.64 CONCLUSIONS During 1990-1998, the output result of GIS interpretation shows that: The total area of forest degradation was 199.31 ha (24.91 ha annually). In more specific terms, the following results were noted: Forest degradation was 34.80% of total area at the slope range 15 0 -25 0 and 37.10% at the slope range 25 0 -35 0 ; 31.70% of total area of forest degradation took place at 500-600 masl and 28.30% at 600-700 masl; 20.40% of total area of forest degradation occurred at the distance range 500-750m and 11.20% at 750- 1000 m distance. The total area of forest restoration was 108.30 ha (13.54 ha annually). Of which, In terms of forest restoration coverage, 43.50% occurred at the slope range 15 0 -25 0 and 35.60% at the slope range 25 0 -35 0 ; 34.10% of forest restoration happened occurred at the elevation range 400m-500m and 33.00 % at the 500m- 600m; and 24.90% of forest restoration occurred at 250-500 m distance, 20.00% at the distance of 100-250 m and 18.00% 500- 750 m from the location of land-use change to the main road. During 1998-2005, the total area of forest degradation was 625.47 ha (89.35 ha annually). Of which, The total area with forest degradation, 37.10% was observed to occur at the slope range 15 0 -25 0 and 34.40% at 250-35 0 slope; 31.70% of the forest degradation area happened at 500-600 masl elevation, 29.50% at 400-500 masl; and 19.10% of the area of forest loss was at the distance of 250-500m and 500-750m, and 9.60% at 1250-1500 m distance); The total area of forest restoration was 657.94 ha (93.99 ha annually). Of which, 37.90% of the total forest restoration area took place mainly at the slope range 15 0 -25 0 and 37.50% at the slope range 15 0 -25 0 ; 27.30% at the elevation 500-600 masl, 24.00% at 600-700 masl and 23.50% at 400-500 masl; and 15.90% of total area of forest restoration was at the distance of 250-500 m to the main road; 13.60% at the distance of 500-750 m and 13.00% at the 750-1000 m. REFERENCES [1.] HUNG, P. T. 2000. Monitoring land use changes with the help of landsat-tm image and geomatic technologies. The case of Loc Chau Commune, Bao Loc District, Lam Dong Province, High Land of Vietnam. International Rice Research Institute, Los Banos, Laguna, Philippines. November 2-3, 2000. [2.] MALYVANH, M. and C. FELDKÖTTER. 2000. Application of remote sensing and GIS for forest cover monitoring in Lao PDR. [3.] WU, Q. H.Q. LI, R. S. WAN, J. PAULUSSEN, Y. HE, M. WANG, B. H. WANG and Z. WANG. 2006. Monitoring and predicting land use change in Beijing using remote sensing and GIS. Landscape and Urban Planning 78 (2006) 322–333. [4.] XIE, Y. and J. FELLOWS. 1996. GIS application in natural reserve management. Page 259-265. In: PETER, WANG J. and Y. XIE. Conserving China‟s Biodiversity (II). Environmental Science Press. Beijing. Số hóa bởi Trung tâm Học liệu - Đại học Thái Nguyên Đàm Việt Bắc và cs Tạp chí KHOA HỌC & CÔNG NGHỆ 77(01): 97 – 102 102 TÓM TẮT BIẾN ĐỘNG SỬ DỤNG ĐẤT LÂM NGHIỆP TẠI XÃ NGỌC PHÁI, HUYỆN CHỢ ĐỒN, TỈNH BẮC KẠN, VIỆT NAM (1990-2005) Đàm Việt Bắc, Đàm Xuân Vận* Trường Đại học Nông lâm – ĐH Thái Nguyên Nghiên cứu đƣợc tiến hành tại xã Ngọc Phái, huyện Chợ Đồn, tỉnh Bắc Kạn, Việt Nam. Mục tiêu của nghiên cứu là xác định sự thay đổi sử dụng đất trong 15 năm qua (1990-2005) của thời kỳ Đổi mới ở khu vực miền núi phía Bắc Việt Nam. Đối với dữ liệu không gian, việc ứng dụng hệ thống thông tin địa lý (GIS) nhƣ một công cụ để xác định sự biến động sử dụng đất. Ba bản đồ sử dụng đất (1990, 1998 và 2005) đã đƣợc chồng ghép và chia thành hai giai đoạn (1990-1998 và 1998- 2005). Một số bản đồ chuyên đề đƣợc tạo ra nhƣ bản đồ độ dốc, chế độ nƣớc, độ cao và bản đồ giao thông. Hơn nữa, các điểm nghiên cứu đƣợc chia thành các lƣới gồm 204 ô với kích thƣớc 500 mx 500 m/ ô hoặc 25 ha/ ô để xác định số lƣợng và những khu vực, vị trí của sự thay đổi sử dụng đất gắn liền với mức độ ô lƣới. Đối với giai đoạn 1990-1998, tổng diện tích rừng bị suy thoái rừng là 109,31 ha. Điều này xảy ra ở độ dốc 15 ° -35°, độ cao 500-700 và ở khoảng cách 500- 1000m từ vị trí của loại đất thay đổi đến đƣờng chính. Việc phục hồi rừng trong khoảng thời gian này đã đƣợc 108,30 ha chủ yếu ở độ dốc 15 ° -35°, độ cao 400-700 và ở khoảng cách 100-250 m, sau đó là 250-500 m và 500-750 m so với đƣờng chính. Đối với thời kỳ 1998-2005, tổng diện tích rừng suy thoái là 625,47 ha, chủ yếu ở độ dốc 15 ° -35°, độ cao 400-600 và ở khoảng cách 250- 500 m , sau đó là 500-750 m và 750-1000 m so với đƣờng chính. Phục hồi rừng trong khoảng thời gian này đã đƣợc 657,94 ha chủ yếu ở độ dốc 15 ° -35 °, độ cao 400-700 và ở khoảng cách 250- 500 m, sau đó là 500-750 m và 750-1000 m so với đƣờng chính. Từ khóa: Biến động sử dụng đất, khu vực miền núi, miền Bắc Việt Nam * Tel: 0982166696; Email: damxuanvan@yahoo.com Số hóa bởi Trung tâm Học liệu - Đại học Thái Nguyên