sunchoke harvest (99%)

i went to campus this morning to look in on the iuncg and harvest sunchokes as the first step towards fall planting for next season...all but one plant had sufficiently died back ( and so only a 99% harvest) so i took a spading fork and started digging...the plants were stunted all season...only reaching about four feet in height..less than half of what i am accustomed to...and their stunted size was refelcted in the size of the harvest...305 tubers from 17 plants...compared to the 800 to 900 i have experienced in the past...true, one plant had 24 tubers attached to it at the roots...and that had radiated out on rhizomes...one reflection of past harvests...there is still one plant left to harvest..it's still flowering but it has to come out because next year's plants are here and need in the garden tomorrow...i buried as much of the organic matter from the plants as i could and carted the harvest home ( to bury for storage ) in my buckets...so...is the skimpy harvest due to the weird weather ( read climate change ) and its impact on a native species...or is it because of a small population representing the third generation removed form the original planting stunted by a lack of sufficient gene flow? climate or genetic diversity? more planting ( next year at home only ) and more observation...this is srill a long-term project