Forest disturbance spectrum of the Amazon
Tropical forests play an important role in global carbon cycle by storing and potentially sequestering a large amount of carbon and are currently considered for climate mitigation policies associated with REDD (Reduced Emission from Deforestation and Degradation). However, recent studies show that there is a large uncertainty on both the stock and dynamics of these forests associated with patterns of tree mortality from natural disturbances. Based on a forest census network of approximately 150 forests plots, Amazon forests constitute a ~0.6 Pg C y-1 sink. The size of this sink has been questioned because frequent large disturbances would invalidate the interpretation of the sparse plot network. We characterize the spectrum of forest disturbance across the entire Amazon basin based on previously published data and we assess the implications of this spectrum on the tropical old-growth forest carbon sink. We use records of biomass changes from a spatially distributed forest census network in the Amazon supplemented by two large forest plot surveys in the Eastern Amazon (53 ha and 114 ha) and an analysis of multiple satellite images to map, detect and estimate the severity of large wind disturbances (blow-downs). We found two disjoint disturbance regimes – small-scale tree-fall gaps within the range of 0.01-0.1ha and rare larger-scale disturbances caused by severe winds predominantly in the western Amazon. Small disturbances (0.01-0.1 ha) are responsible for above-ground biomass losses of about 2.5 Pg C y-1 over the entire Amazon region, but large-scale disturbances for only 0.01 Pg C y-1 because they are extremely rare. Results of a simple stochastic forest simulator based on growth statistics from the forest census and the basin-wide disturbance spectrum indicate that rare larges disturbances do not change the estimates of the positive growth rate trends of old-growth forests previously reported.
Earth Sciences, Earth Systems Research Center
NASA Terrestrial Ecology Science Team Meeting
Espírito-Santo FDB, Gloor M, Keller M, Malhi Y, Saatchi S, Palace M, Frolking S, Phillips O. 2013. Forest disturbance spectrum of the Amazon, NASA Terrestrial Ecology Science Team Meeting, La Jolla, CA, April 30 – May 2, 2013.
Msitu wa Amazon una jukumu muhimu katika mzunguko wa kaboni ulimwenguni kwa kuhifadhi na uwezekano wa kuunganisha kiasi kikubwa cha kaboni na kwa sasa unafikiriwa kwa sera za kupunguza hali ya hewa zinazohusiana na REDD (Kupunguzwa kwa Uzalishaji kutoka kwa Uharibifu wa Misitu na Uharibifu). Hata hivyo, utafiti wa hivi karibuni unaonyesha kwamba kuna kutokuwa na uhakika mkubwa juu ya hifadhi na nguvu ya misitu hii kuhusishwa na mifumo ya vifo vya miti kutokana na usumbufu wa asili. Kulingana na mtandao wa sensa ya misitu ya karibu 150 ya misitu, misitu ya Amazon inaunda ~ 0.6 Pg C y-1 sink. Ukubwa wa sink hii imekuwa swali kwa sababu mara kwa mara usumbufu mkubwa ingekuwa invalidate tafsiri ya mtandao sparse njama. "Tunaelezea wigo wa usumbufu wa misitu katika bonde lote la Amazon kulingana na data zilizochapishwa hapo awali na tunatathmini athari za wigo huu kwenye sinki ya kaboni ya misitu ya kitropiki ya zamani. """ Kwa mfano, utafiti wa mabadiliko ya biomass kutoka kwa mtandao wa sensa ya misitu ya Amazon, iliyoongezwa na uchunguzi wa misitu miwili kubwa katika Amazon ya Mashariki (53 ha na 114 ha) na uchambuzi wa picha nyingi za satelaiti, ili kugundua na kukadiria ukali wa usumbufu mkubwa wa upepo. "Tunapata mifumo miwili ya usumbufu: ""mapengo madogo ya kuanguka kwa miti ndani ya safu ya 0.01 - 0.1ha na usumbufu mdogo wa kiwango kikubwa unaosababishwa na upepo mkali hasa katika Amazon ya magharibi.""" Uharibifu mdogo wa ardhi (ha 0.01 - 0.1) unaathiri hasara ya biomass ya juu ya ardhi ya 2.5 Pg CY 1 katika eneo lote la Amazon, lakini uharibifu mkubwa wa 0.01 Pg CY 1 ni nadra sana. Matokeo ya simulator rahisi stochastic misitu kulingana na takwimu za ukuaji kutoka sensa misitu na msukumo wa msukumo wa bonde nzima yanaonyesha kwamba msukumo mkubwa wa kawaida haubadili makadirio ya mwelekeo wa kasi ya ukuaji wa misitu ya zamani iliyoripotiwa hapo awali. NASA Terrestrial Ecology Science Team Meeting Espiritu Santo, GLOOR, M. Keller, M. Malhi, S. Saatchi, Palace, M. Frolking, S. Phillips, O. Mwaka 2013 Mkutano wa Timu ya Sayansi ya Ekolojia ya Ardhi ya NASA, La Jolla, CA, Aprili 30, 2013