除了直接取水,半干旱和干旱地区的自然水资源短缺可能会因人类辅助植被组成的变化而进一步加剧,包括非本地植物物种的入侵。在干燥的大裂谷中,比较了入侵的Prosopisjuliflora与本地Senegaliasenegal物种的取水,埃塞俄比亚。蒸腾速率使用热比法对6棵树分别进行了量化。julifora和S.senegal,他们在同一农业生态学中彼此相邻。朱草树的用水量范围为1至26L/天(平均4.74±1.97),和S.Senegal树从1到38L/天(在两个研究年中平均为5.48±5.29)。对于这两个物种来说,土壤热,潜热,土壤水分状况影响树木的汁液流动速率;此外,朱草树的用水量与蒸汽压亏缺有关,表明较高的蒸汽压赤字导致朱立花较高的取水量。纯朱立叶酵母和塞内加尔链球菌的树种密度,每公顷有1200-1600棵树和400-600棵树,分别。在支架上,胡立草消耗约6636升/天/公顷(蒸腾作用:每年242毫米),塞内加尔林分消耗2723升/天/公顷(蒸腾作用:每年87毫米)。也就是说,Juliflora消耗的水是S.Senegal的三倍,由于两个原因:(1)朱草分株比塞内加尔分株多茎,然后密度较大的林分比密度较小的本地物种消耗更多的水,(2)朱草是常绿的,全年用水,而塞内加尔则在干旱高峰期脱落叶子。我们的研究结果表明,与塞内加尔相比,胡立草的入侵对埃塞俄比亚旱地的地下水资源造成了严重影响,对生态系统服务和农村生计产生直接和间接影响。
Besides direct water abstraction, natural water scarcity in semi-arid and arid regions may be further exacerbated by human-assisted changes in vegetation composition, including the invasion by non-native plant species. Water abstraction by the invasive tree Prosopis juliflora and by the native Senegalia senegal was compared in the dry Great Rift Valley, Ethiopia. Transpiration rates were quantified using the heat ratio method on six trees each of P. julifora and S. senegal, growing adjacent to each other in the same environment. Water use for P. juliflora trees ranges from 1 to 26 L/day (an average of 4.74 ± 1.97), and that of S. senegal trees from 1 to 38 L/day (an average of 5.48 ± 5.29 during two
study years). For both species, soil heat, latent heat, and soil moisture status influenced the rates of sap flow of trees; in addition, water use by P. juliflora trees was related to vapor pressure deficit; the higher the vapor pressure deficit, the higher the water abstraction by P. juliflora. Stand densities of pure P. juliflora and S. senegal were 1200-1600 trees and 400-600 trees per ha, respectively. At the stand scale, P. juliflora consumed approximately 6636 L/day/ha (transpiration: 242 mm per year) and S. senegal stands consumed 2723 L/day/ha (transpiration: 87 mm per year). That is, P. juliflora stands consumed three times more water than S. senegal stands, because of two reasons: (1) P. juliflora stands are denser than S. senegal stands, and denser stands consume more water than less dense stands, and (2) P. juliflora is evergreen and uses water all year-round, while S. senegal sheds its leaves during the peak dry seasons. Our findings suggest that, compared to S. senegal, P. juliflora invasion results in severe impacts on groundwater resources of the drylands of Ethiopia, with direct and indirect consequences to ecosystem services and rural livelihoods.