UMary Allen
Umuthi isitshalo esinokhuni: isitshalo esinezinkuni, esikhula eside esitholakala cishe kuwo wonke amazwe emhlabeni. Iqukethe izimpande, isiqu somuthi, kanye nomqhele wesihlahla onamaqabunga anamaqabunga noma inaliti. Izihlahla eziningi zihlangene zakha ihlathi.
Ezinye izihlahla ziphila amakhulu eminyaka, ezinye ngisho nangaphezu kweminyaka eyi-1000. Izihlahla azikwazi nje ukuguga kakhulu kodwa futhi zibe zinkulu kakhulu: Isihlahla esikhulu kunazo zonke esisekhona nanamuhla yi-sequoia ethi “Hyperion” enobude besiqu obungaphezu kwamamitha ayi-115. Itholakala eRedwood National Park eCalifornia, eU.SA.
Izihlahla zingahlanganiswa ngezindlela eziningi. Okuyisisekelo kakhulu ukuhlukaniswa kwezihlahla ze-coniferous ezifana ne-pine noma i-fir nezihlahla eziphukayo njenge-maple, i-birch, i-beech, i-chestnut, noma i-linden. Izihlahla zethu ezivuthulukayo zichitha amaqabunga azo njalo ekwindla, ambalwa kuphela ama-conifers enza lokhu, isibonelo, ama-larches. Umehluko wenziwa futhi phakathi kwezinkuni ezishisayo nezinye. Izinkuni zasezindaweni ezishisayo azinazo izindandatho zokukhula futhi zivame ukuba lukhuni.
Eduze nenkabazwe, izihlahla zikhula ngokufanayo unyaka wonke ngenxa yokuthi azikho izinkathi zonyaka. Kwamanye amazwe, izihlahla zikhula ngokushesha ehlobo futhi kancane ebusika. Nakhu okubonayo lapho ugawula isihlahla: isiqu siveza izindandatho ezifana namagagasi lapho uphonsa itshe emanzini, elinye lingaphandle kwelinye. Lezi zindandatho zonyaka zakha ngoba isihlahla sikhula ngokushesha ehlobo. Lokhu kudala indandatho ebanzi, ekhanyayo okhunini. Nokho, ebusika, kuvela indandatho encane kuphela yokhuni oluqinile, olumnyama.
Ososayensi bazisebenzisa kanjani izindandatho zonyaka?
Noma yimuphi umntwana angenza umsebenzi wesayensi olula: ukubala amasongo esihlahleni esisanda kugawulwa noma esiqwini. Uyazi kakade isihlahla sasineminyaka emingaki sigawulwa.
Nokho, ngokuvamile umuntu angathanda ukwazi ukuthi isakhiwo sidala kangakanani. Lokhu kunganqunywa ngemishayo yokhuni etholakala esakhiweni. Kufanele ubhoboze imbobo ensikeni bese ukhipha i-drill core. Inomumo wekhoni ende. Ungabona izindandatho zonyaka kuwo.
Ehlobo elihle, isihlahla ngasinye sifaka indandatho ebanzi yonyaka, ehlobo elibi, elincane. Ososayensi baqophe lokhu kulandelana kumathebula noma imidwebo. Uma manje unomgogodla onjalo wokubhoboza, ungawuqhathanisa namathebula aziwayo kanye nemifanekiso. Ngale ndlela ungathola ukuthi isihlahla sagawulwa ngamuphi unyaka. Ngokuvamile, ugodo lwalufakwa endlini ngemva konyaka owodwa kuya kwemibili isihlahla sigawuliwe. Indlela yokuthola unyaka esakhiwe ngawo isakhiwo. Le sayensi ibizwa ngokuthi "dendrochronology". Lokho kuvela olimini lwesiGreki. "Dendro" kusho "ukhuni". Igama elithi “Chronology” lisho “ukulandelana kwesikhathi”.