VectorPlot3D[{x, y, z}, {x, -1, 1}, {y, -1, 1}, {z, -1, 1}]
Now you can either use ViewPoint
VectorPlot3D[{x, y, z}, {x, -1, 1}, {y, -1, 1}, {z, -1, 1},
ViewPoint -> {0, 0, 200}]
or define a very small z-range
VectorPlot3D[{x, y, z}, {x, -1, 1}, {y, -1, 1}, {z, -0.001, 0.001}]
Grid[{
VectorPlot3D[{x, y, z}, {x, -1, 1}, {y, -1, 1}, {z, ##},
VectorColorFunction -> "ThermometerColors",
PlotTheme -> "Marketing",
ImageSize -> 300] & @@@
{{-0.2, -0.199}, {-0.001, 0.001}, {0.199, 0.2}}
}]
If you dare and have V10 you could also use ClipPlanes:
VectorPlot3D[{x, y, z}, {x, -1, 1}, {y, -1, 1}, {z, -1, 1},
VectorColorFunction -> "Rainbow",
VectorStyle -> "Arrow3D",
PlotTheme -> "Marketing",
ImageSize -> 600,
ClipPlanes -> {{0, 0, -10, -5}}]
