Abramsky Zvika
Natural Resource Ecology Laboratory, Colorado State University, 80523, Fort Collins, CO, USA.
Oecologia. 1978 Jan;34(2):113-123. doi: 10.1007/BF00345160.
The abundance of food in natural 1-ha plot of shortgrass prairie was artificially manipulated by adding alfalfa pellets and whole oats on a regular schedule. The small mammal species naturally inhabiting the manipulated food plot did not respond in either their density or weight to the supplemented food. However, a new specialized seed-eating species, Dipodomys ordii, invaded the food plot and persisted in relatively high density. As a result of this colonization, species diversity was significantly higher on the food plot relative to the unmanipulated control plot. In a second experiment, application of water and nitrogen to two 1-ha plots of shortgrass prairie resulted in increased productivity. However, the increased production on this latter treatment was associated with vegetation growth and thus major changes in habitat structural characteristics relative to the control treatment. Two new species, Microtus ochrogaster and Reithrodontomys megalotis, colonized the nitrogen+water treatment, but other small mammal species "resident" to the shortgrass prairie largely avoided this treatment. As a result of this manipulation, species diversity was significantly lower than the species diversity on the control treatment. These two results agree with the MacArthur prediction regarding how species diversity responds to an increase in production of scarce resources without changes in other habitat variables, and to an increase in productivity associated with changes in other habitat variables.
在天然的1公顷矮草草原地块中，通过定期添加苜蓿颗粒和整粒燕麦，人为控制了食物的丰富程度。自然栖息在这片人为控制食物的地块中的小型哺乳动物物种，其密度和体重对补充食物均无反应。然而，一种新的专门以种子为食的物种——奥氏更格卢鼠，侵入了该食物地块，并以相对较高的密度持续存在。由于这种物种的定殖，该食物地块的物种多样性相对于未进行人为控制的对照地块显著更高。在第二项实验中，对两块1公顷的矮草草原地块施加水和氮，提高了生产力。然而，后一种处理方式下产量的增加与植被生长有关，因此相对于对照处理，栖息地结构特征发生了重大变化。两种新物种——橙腹田鼠和巨耳稻鼠，在氮 + 水处理地块定殖，但矮草草原的其他“常驻”小型哺乳动物物种大多避开了这种处理方式。由于这种人为控制，该处理方式下的物种多样性显著低于对照处理方式下的物种多样性。这两个结果与麦克阿瑟关于物种多样性如何响应稀缺资源产量增加（其他栖息地变量不变）以及与其他栖息地变量变化相关的生产力增加的预测一致。
