Study On The Soil And Water Conservation Ecological Services Under Different Land Use Patterns In Alpine Area

The study on the soil and water conservation ecological services under different land use patterns was conducted in Tianzhu, the alpine meadow area in the eastern part of Qilian Mountains. Five land use patterns, including naturally restored abandoned cropland (NRAC), abandoned cropland (AC), slope cropland (SC), sowed grassland (SG) and natural grassland (NG), were designed to study the impacts of different treatments on soil and water conservation and ecological service functions, including vegetation productivity, biodiversity maintenance, water conservation, soil conservation, carbon sequestration and wind erosion. The main results were as follows:1) The impacts of different land use patterns on the vegetation and soil properties were significant. The vegetation features and soil properties in nature grassland were better than any other land use patterns, while the ground vegetation and soil physical-chemical characteristics in slope cropland and abandoned cropland were the worse.2) The differences of aboveground and underground biomass among 5 types of land use patterns were significant. The order of aboveground biomass was SC (369.6 g/m2) > SG (274.2 g/m2) > NG (211.1 g/m2) > NRAC (176.4 g/m2) > AC (66.8 g/m2). And it was NG (2928.8 g/m2) > SG (738.3 g/m2) > SC (315.8 g/m2) > NRAC (296.3 g/m2) > AC (62.9 g/m2) for underground biomass. The following relationships were found: a logarithmic function relationship between underground biomass and vegetation coverage; a quadratic function relationship between underground biomass and species number. The aboveground biomass was significantly (P<0.05) correlated with vegetation coverage, the underground was significantly (P<0.05) correlated with species and vegetation coverage. The order of ecosystem product services was SC > SG > NG > NRAC > AC.3) Among different land use patterns, the species richness of NG was highest (13), NRAC was next (11), SC and AC were the lowest (7). The ecological dominance and diversity of NG was highest and SC was lowest. The uniformity index of NRAC was the highest (0.51) and SC was the lowest (0.32). And the order was NG > NRAC > SG > SC > AC.4) The storage of soil organic carbon in NG was the highest (5.269 kg/m2) and NRAC was the lowest (1.826 kg/m2). And that was close between SG and AC. The total storage of soil organic carbon within 0 to 30 cm soil layer was NG (15.558 kg/m2) > AC (7.706 kg/m2) > SG (7.559 kg/m2) > SC (6.076 kg/m2) > NRAC (5.477 kg/m2). The storage of soil organic carbon within 0 to 20 cm played an important role in the whole storage capacity of soil organic carbon. The storage capacity of soil organic carbon was NG > AC > SG > SC > NRAC.5) The maximum moisture holding capacity distribution ranged from 681.966 t/ha to 592.93 t/ha in different land use patterns. The capillary moisture distribution ranged from 537.52 t/ha to 622.207 t/ha. The non-capillary moisture distribution ranged from 36.019 t/ha to 62.894 t/ha. The soil water capacity of NG was the highest, while the performance of NRAC was the worse. The ground runoff of AC was the highest (2788.68 m3/ha), and that of NRAC was the next (2073.03 m3/ha), NG was the lowest (581.84 m3/ha). Human activity was the main factor affecting ground runoff. The order of water conservation in different land use patterns was NG > SC > SG > NRAC > AC.6) The soil erosion distribution ranged from 0.037 t/ha to 0.208 t/ha in different land use patterns. The order of soil erosion was AC (0.208 t/ha) > SC (0.155 t/ha) > NRAC (0.139t/ha) > SG (0.121t/ha) > NG (0.037 t/ha). The value of enrichment ratio of soil nutrients was different in different land use patterns. The characteristics of soil nutrient loss showed that high fertility soil lost more nutrients than low fertility soil. The soil erosion modulus of AC was the highest (104.05 t/km2·a), and NG was the lowest (18.308 t/km2·a). Main factor of soil erosion modulus was ground runoff. The order of soil conservation in different land use patterns was NG > SG > NRAC > SC > AC.7) The threshold of wind erosion velocity for SG was the biggest (16m/s),SC and NG were the next (14m/s),AC and NRAC was the smallest (12m/s). The results indicated that the rate of wind erosion positively interrelates with the wind speed. The rate of wind erosion increased with the increasing of wind velocity. A power function relationship was found between wind erosion rate and wind velocity under different land use patterns. The order of the dustfall amount within 0 to 20 cm of aboveground was NRAC > AC > NG > SC > SC. The order of resistance to wind erosion and soil holding capacity of 5 patterns was NRAC = NG > SG > SC > AC.