Thoughts on fire spread from lower elevation grasslands to higher elevation forests, which is a research focus of the NAM Macrosystems proposal:

There are multiple things to consider:
1. Seasonality of grassland fires
2. Climate factors (now, and in the "future") that drive both grassland fires and upper elevation fires (e.g., 2005 Cave Creek fires around Phoenix were largely fueled by a wet winter (that year) that grew invasive bromes.  These conditions (wet winter) inhibit fire spread in upper elevations during that year.  Therefore, under present (and historical) climate conditions, increase in invasives (tied to winter precip) in lowere elevations wouldn't be expected to affect the upper elevations.  Top-down (climate) drivers over-ride bottom up fuel loads and ignitions.  Under future climate scenarios, it might be possible to have a wet winter that grew fuels down low, then a dry enough spring and pre-monsoon period that cured the fuels down low AND DRIED OUT the already abundant fuels in the conifer forests (although not likely the highest elevation spruce-fir).  It could be possible that invasives in the PJ (e.g., cheatgrass in Mesa Verde) couuld fuel fires (after wet winters), because this lowere forest border could dry out quicker and be ready to burn after a wet winter, followed by the usual dry pre-monsoon period.  Would live (canopy) fuel moistures be ready to burn in june (i.e., carry crown fire) after a wet winter?


3. Invasives in the conifer forest could(?) change things in the future, because they cure out faster than other fuels.  So maybe there will be bromes in pipo (or even mixed con) soon?