Climate seasonality limits leaf carbon assimilation and wood productivity in tropical forests

The seasonal climate drivers of the carbon cycle in tropical forests remain poorly known, although these forests account for more carbon assimilation and storage than any other terrestrial ecosystem. Based on a unique combination of seasonal pan-tropical data sets from 89 experimental sites (68 include aboveground wood productivity measurements and 35 litter productivity measurements), their associated canopy photosynthetic capacity (enhanced vegetation index, EVI) and climate, we ask how carbon assimilation and aboveground allocation are related to climate seasonality in tropical forests and how they interact in the seasonal carbon cycle. We found that canopy photosynthetic capacity seasonality responds positively to precipitation when rainfall is  < 2000 mm yr⁻¹ (water-limited forests) and to radiation otherwise (light-limited forests). On the other hand, independent of climate limitations, wood productivity and litterfall are driven by seasonal variation in precipitation and evapotranspiration, respectively. Consequently, light-limited forests present an asynchronism between canopy photosynthetic capacity and wood productivity. First-order control by precipitation likely indicates a decrease in tropical forest productivity in a drier climate in water-limited forest, and in current light-limited forest with future rainfall  < 2000 mm yr⁻¹

Diameter crowth variation for miombo tree species in Kitulang’alo forest reserve, Morogoro Tanzania

With the aim of developing an understanding of diameter growth variation in miombo tree species, this study examines the diameter growth of 53 selected trees from twelve (12) species using dendrometer bands in Kitulang’alo Forest Reserve, Morogoro Tanzania. The selected tree species included Julbernardia globiflora, Brachystergia boehmii, Combretum molle, Dalbergia melanoxylon, Pterocarpus species, Pteliopsis myritifolius, Xeroderris stulhumanii, Diospyros kirkii and Acacia nigrescens, Acacia senegal, Acacia robusta and other Acacia species. The study was done from July 2007 to December 2010. The study complements dendrometer band growth increment data by caliper based method to allow comparison of the two methods in measuring diameter growth. The study revealed that diameter growth rates vary significantly between and within tree species, and also in relation to age, season and microclimatic conditions of the forest. When fitted to nonlinear growth models, parameters were found to be significant Julbernardia globiflora, Brachystergia boehmii and all Acacia species. while non-significant to the rest of the studied species (P>0.05). The study also, found no significant difference between the dendrometer band and the calliper method in measuring diameter increment. However, the band dendrometer method is recommended for short term diameter increment studies (daily to monthly fluctuations) while the calliper method is suitable for long term monitoring of diameter increment studies. The use of high quality dendrometer bands is ideal for quality diameter increment data

Tree growth dynamics and ecological recovery in Kitulangalo Miombo woodlands, Morogoro Tanzania

This research focuses on stand dynamics and ecological recovery in miombo woodlands, Morogoro, Tanzania. The study uses the Kitulangalo Permanent Sample Plots (PSPs) to analyse tree species’ site-specific growth, regeneration dynamics, and stand development using empirical and modeling approaches. The high number of tree species in miombo necessitated the formulation of three species groups involving 1) trees that grow relatively rapidly to be dominants in top canopy layers 2) trees that stay mainly in the lower and middle canopy levels and 3) trees that grow slowly but persistently and may eventually rise to dominant and codominant canopy positions applied in studies I and III. Study III also applies three harvesting alternatives, which align with the recommended harvesting practices for these woodlands. Diameter increment varied with the change in basal area growth across species groups, reaching a maximum of 3.2 cm (group 1) during 2008-2016. Density-dependent mortality and ingrowth also varied with species group as higher mortality rates dominated the lower and middle canopy layers due to asymmetrical competitions. Fencing the plots prompted thick grass cover. The drop in the total number of regeneration stems and the simultaneous increase in the number of main stems in fenced areas and dense plots indicated a self-thinning process induced by competition. This is linked to multi-stem regeneration undergoing a morphological transformation into single-stem saplings (main stems) and eventually becoming small trees. Harvesting intensity, density-dependent mortality, and ingrowth regulated stand basal area and therefore stand growth and development during the simulation. Stand structural development was dominated by species groups 1 and 2, indicating sustainability in species composition and structures. Stand development was affected by the addition of new stems of each species in each simulation year. Miombo stands have demonstrated the potential to attain a steady-state condition over the medium-term under-regulated stand conditions and silvicultural treatments. The developed models, treatments, and harvesting alternatives may be limited in application to Kitulangalo and similar lowland miombo woodlands in Tanzania. Future studies concerning stand conditions, silvicultural treatments, and harvesting alternatives are vital for a better understanding of stand dynamics in miombo woodlands in Tanzania. Keywords: Forest disturbance, tree growth and stand dynamics, regeneration dynamics, silvicultural treatment, harvesting alternative, miombo woodlandsTutkimus käsittelu puuston dynamiikkaa ja ekologista palautumista miombometsissä Morogorossa, Tansaniassa. Tutkimuksessa käytettiin Kitulangalon suojelumetsässä sijaitsevilta pysyviltä koealoilta hankittuja aineistoja metsiköiden ja puiden kasvun, uudistumisdynamiikan ja puuston kehityksen analysointiin mm. empiiristen mallien avulla. Puulajien suuri määrä edellytti kolmen lajiryhmän muodostamista: 1) puut, jotka kasvavat suhteellisen nopeasti hallitseviksi ylimmissä latvuskerroksissa 2) puut, jotka pysyvät pääasiassa alempien ja keskimmäisten latvuskerrosten tasolla ja 3) hitaasti mutta vakaasti kasvavat puut, jotka voivat lopulta nousta hallitseviin ja latvuskerroksiin. Malleilla simuloitiin miombometsien kehitystä erilaisissa käsittelyvaihtoehdoissa. Puun läpimitan kasvu oli nopeinta puulajiryhmässä 1, jossa 8 vuoden kasvun maksimirvo oli 3,2 cm. Tiheydestä riippuvainen kuolleisuus ja sisäänkasvu (niiden puiden määrä jotka saavuttivat 5 cm läpimitan 8-vuotisen tutkimusjakson aikana) vaihtelivat myös lajiryhmittäin, ja kuolleisuus oli suurinta alimpien ja keskimmäisten latvuskerrosten puissa joihin kohdistui epäsymmetrinen kilpailu ylempien latvuskerrosten taholta. Koealojen aitaaminen, jolla estettiin karjan laiduntaminen, johti pintakasvillisuuden voimakkaaseen rehevöitymiseen, taimien kokonaisrunkoluvun laskuun ja samanaikaiseen valtataimien määrän kasvuun Poimintahakkuiden voimakkuus, tiheydestä riippuva kuolleisuus ja puiden kasvu säätelivät puuston kehitystä ja tiheyttä 99-vuotta käsittäneen simulointijakson aikana. Lajiryhmät 1 ja 2 olivat hallitsevassa asemassa kaikissa simulointivaihtoehdoissa, mikä ilmensipuuston rakenteen ja puulajikoostumuksen resilienssiä. Tulokset viittasivat miombometsien hyvään palautumiskykyyn voimakkaiden säätelemättömien hakkuiden jälkeen. Koska tutkimuksen tulokset perustuivat vain Kitulangalon alueelta hankittuihin aineistoihin, niiden suora yleistettävyys rajoittuu Kitulangalon olosuhteita vastaaviin tasankomaiden miombo-metsiin Tansaniassa. Laajemmat puuston rakennetta ja dynamiikkaa, metsänhoitomenetelmiä ja käsittelyvaihtoehtoja koskevat tutkimukset ovat elintärkeitä, jotta ymmärrettäisiin paremmin miombometsien tilaa ja dynamiikkaa Tansanian ja koko eteläisen Afrikan alueella. Asiasanat: Metsähäiriöt, puiden kasvu ja puuston dynamiikka, uudistumisdynamiikka, metsänhoito, korjuuvaihtoehto, miombo-metsä

Diameter crowth variation for miombo tree species in Kitulang’alo forest reserve, Morogoro Tanzania

With the aim of developing an understanding of diameter growth variation in miombo tree species, this study examines the diameter growth of 53 selected trees from twelve (12) species using dendrometer bands in Kitulang’alo Forest Reserve, Morogoro Tanzania. The selected tree species included Julbernardia globiflora, Brachystergia boehmii, Combretum molle, Dalbergia melanoxylon, Pterocarpus species, Pteliopsis myritifolius, Xeroderris stulhumanii, Diospyros kirkii and Acacia nigrescens, Acacia senegal, Acacia robusta and other Acacia species. The study was done from July 2007 to December 2010. The study complements dendrometer band growth increment data by caliper based method to allow comparison of the two methods in measuring diameter growth. The study revealed that diameter growth rates vary significantly between and within tree species, and also in relation to age, season and microclimatic conditions of the forest. When fitted to nonlinear growth models, parameters were found to be significant Julbernardia globiflora, Brachystergia boehmii and all Acacia species. while non-significant to the rest of the studied species (P>0.05). The study also, found no significant difference between the dendrometer band and the calliper method in measuring diameter increment. However, the band dendrometer method is recommended for short term diameter increment studies (daily to monthly fluctuations) while the calliper method is suitable for long term monitoring of diameter increment studies. The use of high quality dendrometer bands is ideal for quality diameter increment data

Skin maculae, chronic diarrhea, cachexia, and splenomegaly-Late presentation of the first autochthonous case of visceral leishmaniasis in Tanzania.

A 20-year-old man from Simanjiro district in northern Tanzania presented with a 3-year history of splenomegaly, fatigue, cachexia, skin maculae, and recent onset of watery diarrhea at Kilimanjaro Christian Medical Centre (KCMC) in Northern Tanzania. Due to laboratory findings of pancytopenia, diagnostic workup included bone marrow aspiration cytology and biopsy. Although the rapid test (IT LEISH, rK39 RDT) was negative, blood smear showed amastigote forms of leishmaniasis in macrophages. Repeat bone marrow aspiration and PCR eventually confirmed visceral leishmaniasis (VL). The patient denied travel to known endemic areas of VL. Treatment was initiated with Amphotericin B, but the patient died on the fourth day of treatment from respiratory insufficiency. An autopsy revealed massive organ manifestations of VL. This is the first reported autochthonous case of VL in Tanzania. Clark and colleagues detected the vector Phlebotomus martini in Northern Tanzania in 2013, in a region bordering the district of our patient. The negative rapid test draws attention to the fact that sensitivity and specificity were found to be low in East African VL patients as displayed earlier by a Kenyan study. Therefore, tissue samples (spleen or bone marrow) remain necessary for diagnosis. The variety of symptoms in this presented case was remarkable, including the occurrence of post-kala-azar dermal leishmaniasis (PKDL) and VL at the same time. This has been described in East African VL cases before as well as the occurrence of chronic diarrhea. An elongated undiagnosed period likely led to a mixed clinical picture that included hepato-splenomegaly, PKDL, cachexia, and diarrhea

WagnerClimateSeasonalityLimitsSupplementalTablesandFigures.pdf

The seasonal climate drivers of the carbon cycle in tropical forests remain poorly known, although these forests account for more carbon assimilation and storage than any other terrestrial ecosystem. Based on a unique combination of seasonal pan-tropical data sets from 89 experimental sites (68 include aboveground wood productivity measurements and 35 litter productivity measurements), their associated canopy photosynthetic capacity (enhanced vegetation index, EVI) and climate, we ask how carbon assimilation and aboveground allocation are related to climate seasonality in tropical forests and how they interact in the seasonal carbon cycle. We found that canopy photosynthetic capacity seasonality responds positively to precipitation when rainfall is  < 2000 mm yr⁻¹ (water-limited forests) and to radiation otherwise (light-limited forests). On the other hand, independent of climate limitations, wood productivity and litterfall are driven by seasonal variation in precipitation and evapotranspiration, respectively. Consequently, light-limited forests present an asynchronism between canopy photosynthetic capacity and wood productivity. First-order control by precipitation likely indicates a decrease in tropical forest productivity in a drier climate in water-limited forest, and in current light-limited forest with future rainfall  < 2000 mm yr⁻¹

WagnerClimateSeasonalityLimits.pdf

The seasonal climate drivers of the carbon cycle in tropical forests remain poorly known, although these forests account for more carbon assimilation and storage than any other terrestrial ecosystem. Based on a unique combination of seasonal pan-tropical data sets from 89 experimental sites (68 include aboveground wood productivity measurements and 35 litter productivity measurements), their associated canopy photosynthetic capacity (enhanced vegetation index, EVI) and climate, we ask how carbon assimilation and aboveground allocation are related to climate seasonality in tropical forests and how they interact in the seasonal carbon cycle. We found that canopy photosynthetic capacity seasonality responds positively to precipitation when rainfall is  < 2000 mm yr⁻¹ (water-limited forests) and to radiation otherwise (light-limited forests). On the other hand, independent of climate limitations, wood productivity and litterfall are driven by seasonal variation in precipitation and evapotranspiration, respectively. Consequently, light-limited forests present an asynchronism between canopy photosynthetic capacity and wood productivity. First-order control by precipitation likely indicates a decrease in tropical forest productivity in a drier climate in water-limited forest, and in current light-limited forest with future rainfall  < 2000 mm yr⁻¹