Ososayensi e I-US Forest Service's Pacific Northwest Research Station I-Portland, e-Oregon, isungule imodeli yokubikezela ukuqhuma kwehlumela. Basebenzise ama-Douglas firs ekuhloleni kwabo kodwa futhi benza ucwaningo mayelana nezinye izinhlobo zezilwane ezingaba ngu-100, ngakho balindele ukuthi bakwazi ukulungisa imodeli yezinye izitshalo nezihlahla.
Kokubili amazinga okushisa abandayo nafudumele athinta isikhathi, futhi inhlanganisela ehlukene iveza imiphumela ehlukene — ayihlale inembile. Njengoba kunamahora amaningi okushisa abandayo, izihlahla zidinga amahora ambalwa afudumele ukuze ziqhume. Ngakho-ke ukufudumala kwentwasahlobo kwangaphambili kuzodala ukuqhuma kwehlumela ngaphambili. Uma isihlahla singabanda ngokwanele, sidinga ukufudumala okwengeziwe ukuze siqhume. Ngakho-ke ngaphansi kwezimo ezimangalisayo zokushintsha kwesimo sezulu, ubusika obufudumele bungase busho ukuqhuma kwakamuva.
Izakhi zofuzo nazo ziyadlala. Abacwaningi bazame ama-Douglas firs abavela ngaphesheya kwe-Oregon, Washington, naseCalifornia. Izihlahla ezivela ezindaweni ezibandayo noma ezomile zibonise ukuqhuma kwangaphambili. Izihlahla eziphuma kuleyo migqa zingakhula kangcono ezindaweni lapho abazala bazo abajwayele ukufudumala noma okumanzi behlala khona manje.
Ithimba, eliholwa isazi sehlathi socwaningo u-Connie Harrington, lithemba ukusebenzisa imodeli ukubikezela ukuthi izihlahla zizosabela kanjani ngaphansi kokuqagela okuhlukahlukene kwesimo sezulu. Ngalolo lwazi, abaphathi bomhlaba banganquma ukuthi bazotshala kuphi nokuthi yini, futhi, uma kunesidingo, bahlele amasu okufuduka okusizwayo.