Metsa alustaimestiku seos keskkonnafaktoritega

https://www.ester.ee/record=b5496223*es

Valguse neeldumine taimestikus, fotosünteesivõime ja liikide varjutaluvus: üldised seaduspärad ning erinevused funktsionaalsete gruppide vahel

The general aim of this study was to identify the suites of traits responsible for species shade tolerance and light harvesting in different plant functional groups. In particular, to understand how plant responses to light availability depend on species-specific functional traits in different plant functional groups at common light availability (genotypic plasticity) and within light gradients (phenotypic patterns). The results showed complex interactions between phenotypic plasticity and inherent species-specific differences, influencing the ability of plants to cope with limited light conditions, created by the surrounding vegetation. Alternative strategies, which can be partly explained by dynamics of light availability during leaf life-span, were observed among deciduous and evergreen woody species, graminoids and forbs. (1) In temperate woody flora of the Northern Hemisphere, species shade tolerance was positively related to leaf life-span and negatively related to leaf dry mass per area (LMA), nitrogen content per leaf area (Na) and photosynthetic capacity (Aa). However, there were also remarkable differences between the functional groups as shade tolerance decreased with photosynthetic capacity per leaf dry mass (Am) within deciduous broad-leaved group and increased within evergreen conifers’ group. (2) Within the deciduous tree canopy LMA and Na increased significantly along vertical gradient of light availability. In the herbaceous canopy, on the contrary, LMA and Na were generally not related to current light conditions, reflecting limited re-acclimation potential of mature leaves. (3) Community-level patterns in light capture, biomass and nitrogen partitioning were largely attributable to changes in species composition along a productivity gradient in herbaceous stands. Species, which became dominant at high soil resources had lower tissue nitrogen concentrations (high aNUE) and lower leaf area ratio (LAR), leading to community-level increase in aNUE and decrease in LAR along the productivity gradient. However, some subordinate species increased LAR with increasing soil fertility, indicating that dominant and subordinate species have distinct strategies to cope with increased competition for limited light resource.Minu doktoritöö eesmärgiks oli uurida, kuidas taimelehtede funktsionaalsed tunnused ning maapealse biomassi jaotus sõltuvad valgustingimustest nii liigisiseselt kui liikide vahel. Antud töö tulemuste põhjal võib öelda, et (1) põhjapoolkera parasvöötme puittaimedel on varjutaluvus üldiselt liigispetsiifilise keskmise lehe eluea ja -eripinnaga positiivses seoses ning lämmastikusisalduse ja fotosünteesivõimega (väljendatuna pindalaühiku kohta) negatiivses seoses, kuid funktsionaalsete gruppide siseselt esineb seoses üksikute lehe tunnustega märkimisväärseid erinevusi; (2) puittaimedel on seosed lehe tunnuste (eripind ning klorofülli- ja lämmastikusisaldus) ja valgustingimuste vahel piki lehestikusisest vertikaalset valgusgradienti tugevamad kui rohttaimedel ning (3) rohttaimede lämmastikukasutuse efektiivsuse ja maapealse biomassi jaotuse liigiomased erinevused mõjutavad oluliselt koosluse tasemel avalduvaid seoseid taimkattes neeldunud valgusega

Are Species shade and drought tolerance reflected in leaf-level structural and functional differentiation in Northern Hemisphere temperate woody flora?

Leaf-level determinants of species environmental stress tolerance are still poorly understood. Here, we explored dependencies of species shade (Tshade) and drought (Tdrought) tolerance scores on key leaf structural and functional traits in 339 Northern Hemisphere temperate woody species. In general, Tshade was positively associated with leaf life-span (LL), and negatively with leaf dry mass (MA), nitrogen content (NA), and photosynthetic capacity (AA) per area, while opposite relationships were observed with drought tolerance. Different trait combinations responsible for Tshade and Tdrought were observed among the key plant functional types: deciduous and evergreen broadleaves and evergreen conifers. According to principal component analysis, resource-conserving species with low N content and photosynthetic capacity, and high LL and MA, had higher Tdrought, consistent with the general stress tolerance strategy, whereas variation in Tshade did not concur with the postulated stress tolerance strategy. As drought and shade often interact in natural communities, reverse effects of foliar traits on these key environmental stress tolerances demonstrate that species niche differentiation is inherently constrained in temperate woody species. Different combinations of traits among key plant functional types further explain the contrasting bivariate correlations often observed in studies seeking functional explanation of variation in species environmental tolerances.18 page(s

Veetaseme seire, üleujutuste kaardistamine ja märgalae niiskusrežiim

Projekti RITA1 KAUGSEIRE käigus töötati välja kaugseire andmete töötlemise metoodid/prototüübid, mis võimaldavad parandada mitmeid järgmisi seirerakendusi ja riiklike teenuseid: (1) üleujutuste seire satelliitpiltidel sisemaal ja rannikul; (2) veetaseme seire kasutades altimeetria andmeid; (3) veetaseme prognoosi täpsustamine satelliitaltimeetria andmetega; (4) veekogu ökoloogilise klassi korrektsioon vastavalt veetaseme sesoonsele muutusele; (5) soode niiskus režiimi jälgimine kaugseire meetodiga; (6) maardlate (s.h. turbamaardlate) seire satelliitpiltidelt

Responses of the reflectance indices PRI and NDVI to experimental warming and drought in European shrublands along a north-south climatic gradient

The aim of this study was to evaluate the use of ground-based canopy reflectance measurements to detect 40 changes in physiology and structure of vegetation in response to experimental warming and drought 41 treatment at six European shrublands located along a North–South climatic gradient. We measured canopy 42 reflectance, effective green leaf area index (green LAIe) and chlorophyll fluorescence of dominant species. The 43 treatment effects on green LAIe varied among sites. We calculated three reflectance indices: photochemical 44 reflectance index PRI [531 nm; 570 nm], normalized difference vegetation index NDVI680 [780 nm; 680 nm] 45 using red spectral region, and NDVI570 [780 nm; 570 nm] using the same green spectral region as PRI. All three 46 reflectance indices were significantly related to green LAIe and were able to detect changes in shrubland 47 vegetation among treatments. In general warming treatment increased PRI and drought treatment reduced 48 NDVI values. The significant treatment effect on photochemical efficiency of plants detected with PRI could not 49 be detected by fluorescence measurements. However, we found canopy level measured PRI to be very sensitive 50 to soil reflectance properties especially in vegetation areas with low green LAIe. As both soil reflectance and LAI 51 varied between northern and southern sites it is problematic to draw universal conclusions of climate-derived 52 changes in all vegetation types based merely on PRI measurements. We propose that canopy level PRI 53 measurements can be more useful in areas of dense vegetation and dark soils

A Worldwide analysis of within-canopy variations in leaf structural, chemical and physiological traits across plant functional types

Extensive within-canopy light gradients importantly affect the photosynthetic productivity of leaves in different canopy positions and lead to light-dependent increases in foliage photosynthetic capacity per area (AA). However, the controls on AA variations by changes in underlying traits are poorly known. We constructed an unprecedented worldwide database including 831 within-canopy gradients with standardized light estimates for 304 species belonging to major vascular plant functional types, and analyzed within-canopy variations in 12 key foliage structural, chemical and physiological traits by quantitative separation of the contributions of different traits to photosynthetic acclimation. Although the light-dependent increase in AA is surprisingly similar in different plant functional types, they differ fundamentally in the share of the controls on AA by constituent traits. Species with high rates of canopy development and leaf turnover, exhibiting highly dynamic light environments, actively change AA by nitrogen reallocation among and partitioning within leaves. By contrast, species with slow leaf turnover exhibit a passive AA acclimation response, primarily determined by the acclimation of leaf structure to growth light. This review emphasizes that different combinations of traits are responsible for within-canopy photosynthetic acclimation in different plant functional types, and solves an old enigma of the role of mass- vs area-based traits in vegetation acclimation.21 page(s