Allometric biomass,nutrient and carbon stock models for <Emphasis Type="Italic">Kandelia candel</Emphasis> of the Sundarbans,Bangladesh

Key message

Present study recommends DBH as independent variable of the derived allometric models and Biomass = a + b DBH ² has been selected for total above-ground biomass, nutrients and carbon stock.

Abstract

Kandelia candel (L.) Druce is a shrub to small tree of the Sundarbans mangrove forest of Bangladesh. The aim of the study was to derive the allometric models for estimating above-ground biomass, nutrient and carbon stock in K. candel. A total of eight linear models with 64 regression equations were tested to derive the allometric models for biomass of each part of plant; and nutrients and carbon stock in total above-ground biomass. The best fitted allometric models were selected by considering the values of R ², CV, R _mse, MS_error, S _a, S _b, F value, AICc and Furnival Index. The selected allometric models were Biomass = 0.014 DBH² + 0.03; √Biomass = 0.29 DBH ? 0.21; √Biomass = 0.66 √DBH ? 0.57; √Biomass = 1.19 √DBH ? 1.02; Biomass = 0.21 DBH² + 0.12 for leaves, branches, bark, stem without bark and total above-ground biomass, respectively. The selected allometric models for Nitrogen, Phosphorous, Potassium and Carbon stock in total above-ground biomass were N = 0.39 DBH² + 0.49, P = 0.77 DBH² + 0.14, K = 0.87 DBH² + 0.07 and C = 0.09 DBH² + 0.05, respectively. The derived allometric models have included DBH as a single independent variable, which may give quick and accurate estimation of the above-ground biomass, nutrient and carbon stock in this species. This information may also contribute to a broader study of nutrient cycling, nutrient budgeting and carbon sequestration of the studied forest.

     

Biomass dynamics in a logged forest: the role of wood density

Wood density (WD) is believed to be a key trait in driving growth strategies of tropical forest species, and as it entails the amount of mass per volume of wood, it also tends to correlate with forest carbon stocks. Yet there is relatively little information on how interspecific variation in WD correlates with biomass dynamics at the species and population level. We determined changes in biomass in permanent plots in a logged forest in Vietnam from 2004 to 2012, a period representing the last 8 years of a 30 years logging cycle. We measured diameter at breast height (DBH) and estimated aboveground biomass (AGB) growth, mortality, and net AGB increment (the difference between AGB gains and losses through growth and mortality) per species at the individual and population (i.e. corrected for species abundance) level, and correlated these with WD. At the population level, mean net AGB increment rates were 6.47 Mg ha^?1 year^?1 resulting from a mean AGB growth of 8.30 Mg ha^?1 year^?1, AGB recruitment of 0.67 Mg ha^?1 year^?1 and AGB losses through mortality of 2.50 Mg ha^?1 year^?1. Across species there was a negative relationship between WD and mortality rate, WD and DBH growth rate, and a positive relationship between WD and tree standing biomass. Standing biomass in turn was positively related to AGB growth, and net AGB increment both at the individual and population level. Our findings support the view that high wood density species contribute more to total biomass and indirectly to biomass increment than low wood density species in tropical forests. Maintaining high wood density species thus has potential to increase biomass recovery and carbon sequestration after logging.     

Relationships between tree dimension and coarse root biomass in mixed stands of European beech (Fagus sylvatica L.) and Norway spruce (Picea abies[L.] Karst.)

Relationships between tree parameters above ground and the biomass of the coarse root system were examined in six mixed spruce-beech stands in the Solling Mountain region in northwest Germany. The selected stands were located on comparable sites and covered an age range of 44 to 114 years. Coarse roots (d?\ge?2 mm) of 42 spruce and 27 beech trees were sampled by excavating the entire root system. A linear model with logarithmic transformation of the variables was developed to describe the relationship between the coarse root biomass (CRB, dry weight) and the corresponding tree diameter at breast height (DBH). The coefficients of determination (R ²) attained values between 0.92 for spruce and 0.94 for beech; the logarithmic standard deviation values were between 0.29 and 0.43. A significantly different effect of tree species on the model estimates could not be detected by an analysis of co-variance (ANCOVA). For spruce, the derived relationships were similar to those reported in previous studies, but not for beech. Biomass partitioning in the tree compartments above and below ground differs significantly between spruce (coarse root/shoot ratio 0.16±0.06) and beech (coarse root/shoot ratio 0.10±0.03) in the mixed stands. These results are similar to those given in other studies involving pure spruce and beech stands on comparable sites in the region, although the ratios of pure stands in other regions growing under different site conditions are somewhat higher. Comparing trees of the same DBH classes, root/shoot ratios of spruce are 1.2 to 3 times higher than those of beech. Dominant spruce trees (DBH>60 cm) attained the highest ratios, suppressed beech trees (DBH<10 cm) the lowest. Site conditions of varying climate and soils and interspecific tree competition are likely to affect root/shoot ratio and DBH-coarse root biomass relationships. The greater variability in beech compared with spruce indicates a high 'plasticity' and adaptability of beech carbon allocation. Thus, the derived equations are useful for biomass estimates of coarse roots involving trees of different ages in mixed stands of spruce and beech in the Solling Mountains. However, application of these relationships to stands in other regions would need further testing.     

Allometry of aboveground biomasses in mangrove species in Itamaracá, Pernambuco, Brazil

Allometric equations to estimate aboveground biomass (AGB) and plant part biomasses (PPB) of three mangrove species, Rhizophora mangle, Avicennia schaueriana, and Laguncularia racemosa, were determined in Itamaracá, Pernambuco, Brazil (7°48′44″S and 34°49′39″W). Twenty-three to thirty-six trees of each species, ranging in height (H) from 1.6 to 11.8 m and in diameter, at breast height or above prop roots (D), from 2 to 21 cm, were measured, cut, and separated into stems, branches, leaves, and prop roots. Biomass proportions in each tree part were similar among species, excluding prop roots: stems 37–47%, branches 41–46%, and leaves 11–17%. Prop roots represented 37% of AGB in R. mangle. Tree size had a significant but not large influence on biomass distribution among plant parts: as stem diameters increased the proportions allocated to leaves decreased and those to stems and branches increased. AGB and PPB were significantly related to D and D² × H and the best fittings were obtained with power equations. A few equations from literature fitted the data reasonably well for AGB of one or two of the species but resulted in large errors for the others. Applying the equations to previous measurements of tree diameters in a sample area, AGB for the mangrove site was estimated at 105 Mg ha⁻¹, with 78, 19, and 3% corresponding to biomasses of R. mangle, L. racemosa, and A. schaeuriana trees, respectively.     

Aboveground biomass dynamics of subalpine old-growth forest in the upper reach of the Minjiang River

Biomass estimation of old-growth forests in the upper Minjiang River (UMR) is important in quantifying carbon (C) sequestration and C sink size because majority of the natural forests in UMR are mature or over-mature. Based on the forest resource data from 27 fixed sampling plots that have been surveyed consecutively, the dynamics of the aboveground biomass density (AGBD) were characterized by the allometric relationships, and the space-time variations of the C sink size in the sub-alpine old-growth forests of UMR were explored. Our results showed that 1) the net increase in AGBD was (27.311 ± 15.580) Mg·hm^?2 and the mean annual growth rate and mean annual death rate were (1.930 ± 1.091) and (2.271 ± 1.424) Mg·hm^?2·a^?1 during 1988–2002, respectively. 2) The aboveground biomass (AGB) largely depended on the growth and death rates of the trees with different diameters at the breast height (DBH) classes and the recruitment rate from one DBH class to another as well. The largest increment component of AGB came from the DBH class of 20 to 40 cm, whereas the minimum increment component of AGB was above 80 cm in DBH. The net negative increment of AGB occurred at DBH classes of 40–60 and 60–80 cm. 3) There were space-time variations of AGB in the alpine old-growth forests, indicated by AGB changing over time in the same sampling plot and varying among the locations or plots during the same sampling period. These variations were not only reflected in numerical value but also in positive or negative biomass increment.     

Biomass accumulation and carbon storage of four different aged Sonneratia apetala plantations in Southern China

The objectives of this study were to examine plant biomass accumulation and carbon (C) storage in four different aged Sonneratia apetala plantations in the Leizhou Bay in South China. The allometric equations using diameter at breast height (DBH) and height (H) were developed to quantify plant biomass. The total forest biomass (TFB) of S. apetala plantation at 4, 5, 8, and 10 years old was 47.9, 71.7, 95.9, and 108.1 Mg ha^?1, respectively. The forest biomass C storage in aboveground (AGB) and roots at 4, 5, 8, and 10-year plantation was 19.9, 32.6, 42.0, 49.0 Mg ha^?1, respectively. Soil organic C (SOC) on the top 20 cm of sediments increased by 0.3, 6.8, 27.4, and 35.0 Mg ha^?1after 4, 5, 8, and 10 years of reforestation, respectively. The average annual rate of total carbon storage (TCS) accumulation at 4, 5, 8, and 10-year S. apetala plantation was 5.0, 7.9, 8.7, and 8.4 Mg ha^?1 yr^?1, respectively. The TCS values in this study were underestimated because we only estimated SOC storage on the top 20-cm sediments in these plantations. This study suggests these young S. apetala plantations have the characteristics of fast growth, high biomass accumulation, and high C storage capacity, especially in sediments. They sequestrated C at a high but varying rate over time. The large-scale reforestation of S. apetala plantations in the open coastal mudflats in southern China has great potential to sequestrate more C as well as restore the degraded coastal land. The potential ecological issues associated with the increasing monoculture plantations were discussed. More long-term monitoring and research are needed to further evaluate biomass and C accumulation of S. apetala plantations over time as well as how the increasing distribution of this monoculture plantation will influence the few native mangrove remnants.     

南岭小坑藜蒴栲群落地上部分生物量分配规律

采用皆伐法对南岭小坑750m2天然藜蒴栲群落的生物量进行了实测,该群落有43个树种,其中藜蒴栲为优势种,获得了胸径2.0 cm以上的267株树的树干、枝、叶烘干重数据以及实测的胸径（D）、树高（H）数据。揭示了该森林群落地上部分总生物量(AGB)在森林各层次、各树种及乔木层各器官中的分配规律,并建立了该群落的生物量模型。结果表明,南岭小坑流域藜蒴栲群落地上部分总生物量是131.149 t.hm-2,其中乔木层是129.895 t.hm-2,下木层是1.563 t.hm-2,层间植物是0.267 t.hm-2,凋落物层是2.424 t.hm-2。树干、树枝、树叶生物量分别是乔木层地上部分总生物量的85.0%、10.6%和4.4%。优势树种藜蒴栲和小红栲生物量是乔木层地上部分总生物量的46.3%和9.8%,这说明在早期演替的森林群落中生物量主要集中分布在少数的几个优势种。乔木各径阶（DBH<5,5~10,10~15,15~20,20~25,≥25cm）的生物量占乔木层地上部分总生物量的百分比分别是1.0%, 13.1%,52.2%,26.4%,4.6%和2.7%。天然次生藜蒴栲群落以D为自变量的模型是Wtagb=0.116D2.384,R2=0.934,模型估算值比皆伐实测值低5.0%;以D2H为自变量的总生物量模型是Wtagb=184.274(D2H)0.881,R2=0.952,模型估算值比皆伐实测值低6.9%;这说明针对天然藜蒴栲群落,采用以D为自变量的总生物量模型更为实用。     

岷江上游亚高山林区老龄林地上生物量动态变化

中国川西亚高山森林中的天然林大部分为成过熟的老龄林,对其生物量动态研究有助于了解其碳储量的动态变化规律.利用全国森林资源连续清查的27个固定样地数据,基于地上各器官生物量与树干胸径(D)和树高(h)的异速生长方程,估算了岷江上游亚高林山老龄林地上生物量密度的动态变化特征及其时空变化规律.结果表明,(1)从1988～2002年期间,老龄林地上生物量密度净增量为(27.311±15.580)Mg·hm-2,平均每年增长率为(1.930±1.091 )Mg·hm-2·a-1,平均每年枯损率为(2 271±1.424)Mg·hm-2·a-1;(2)地上生物量变化受各径级保留木生长量、枯损量及进界生长量影响,其中20～40cm径级保留木生长量与生物量净增量最大,>80cm径级生物量增量最小,40～60cm和60～80cm径级生物量在调查期间净增量出现负增长.(3)岷江上游老龄林地上生物量动态变化具有时空异质性,同一样地在不同调查间隔期或同一调查期间不同样地间生物量变化不同,不仅有增量数值大小差异,还表现为生物量增量的正负差异.     

Leaf and flower formation in shoot tips of mangrove trees in Pernambuco, Brazil

Leaves are major components of mangrove productivity, but data on leaf dynamics are scarce. We marked the shoot tips of three species in four sites of a riverine mangrove and monitored leaf formation, senescence and abscission and flower formation. The leaf area and biomass in the mangrove were estimated using phytosociological data. Leaf size and formation were similar among the four sites. The tips of Rhizophora mangle had more leaf scars (41), more leaves present (9.7), a faster leaf formation rate (one every 26 days) and a shorter life span (8.4 months) than those of Avicennia schaueriana (10, 8.1, 48 days and 13.1 months, respectively) and Laguncularia racemosa, except for the shorter life span (15, 6.6, 31 days and 6.8 months, respectively). The proportion of tips that flowered was higher in L. racemosa (13 %) and in R. mangle (11 %) than in A. schaueriana (2 %). The largest biomass of the average R. mangle leaf (0.75 vs. 0.53 and 0.37 g leaf^?1, of L. racemosa and A. schaueriana, respectively) and the highest plant density of this species (2,590 vs. 694 and 202 plant ha^?1, respectively) resulted in it having the greatest leaf productivity (10.6 Mg ha^?1 year^?1 compared to 2.4 Mg ha^?1 year^?1 for L. racemosa and 0.3 Mg ha^?1 year^?1 for A. schaueriana). The total leaf production is higher in this mangrove than most of those reported for other mangroves in the world.     

Fine root production in three zones of secondary mangrove forest in eastern Thailand

Key message

High root productions, especially in the fine roots, estimated by ingrowth cores were confirmed in mangrove forests. The zonal variation in root production was caused by inundation regime and soil temperature.

Abstract

Mangrove forests have high net primary productivity (NPP), and it is well known that these trees allocate high amounts of biomass to their root systems. In particular, fine root production (FRP) comprises a large component of the NPP. However, information on root production remains scarce. We studied FRP in three zones (Avicennia, Rhizophora, and Xylocarpus) of a mangrove forest in eastern Thailand using ingrowth cores (0–30 cm of soil depth). The root biomass and necromass were periodically harvested from the cores and weighed during the one-year study. The FRP was determined by summation of the fine root biomass (FRB) and root necromass. The results showed that the FRB clearly increased in the wet and cool dry seasons. Magnitude of FRB in the Rhizophora and Xylocarpus zones was 1171.07 and 764.23 g/m²/30 cm, respectively. The lowest FRB (292.74 g/m²/30 cm) was recorded in the Avicennia zone locating on the river edge where there is a greater frequency of inundation than the other zones. Root necromass was high in the Rhizophora and Xylocarpus zones, and accumulated noticeably when soil temperatures rapidly declined during the middle of the wet season to cool dry season. However, root necromass in the Avicennia zone varied within a small range. We attributed the small accumulation of root necromass in the Avicennia zone to the relative high soil temperature that likely caused a high root decomposition rate. The average FRP (3.403–4.079 ton/ha/year) accounted for 74.4, 81.5, and 92.4 % of the total root production in the Avicennia, Rhizophora, and Xylocarpus zone, respectively. The root production and causative factors (i.e., soil temperature and inundation regime) are discussed in relation to the carbon cycle of a mangrove forest.

     

基于高分辨率遥感影像的森林地上生物量估算

以南京市紫金山林区为研究区,利用e-Cognition面向对象分类方法,基于光谱和空间信息融合后的IKONOS影像提取单木树冠阳性冠幅(PoCA, Positive crown area)信息,并结合野外实测的样方生物量数据,分别建立了针叶林和阔叶林地上生物量 (AGB, Aboveground Biomass)的遥感估算模型,并利用实测森林生物量数据对模型进行了验证。结果表明,基于遥感影像提取的PoCA与实测AGB存在较好的非线性相关关系,所建针叶林AGB估算模型的可靠性优于阔叶林模型。对建模样本而言,估算的针叶林和阔叶林AGB与观测数据比较的R2分别为0.62 (P<0.01,n=9) 和0.56(P<0.01,n=16)。验证表明,所建AGB估算模型的可靠性较好,估算的针叶林和阔叶林AGB与观测数据比较的R2分别为0.55(P<0.01,n=6) 和0.52(P<0.01,n=10),但当AGB较低时,模型结果偏高,AGB较低时,模型结果偏低。研究说明通过高分辨率遥感数据的融合、提取树冠信息进行生物量估算是可行性的。     

Pre-logging carbon accounts in old-growth forests,via allometry: An example of mixed-forest in Tasmania,Australia

Abstract

Uncertainty in past and future anthropogenic carbon emissions obscures climate change modelling. Available allometrics are insufficient for regional-level accounting of old-growth, pre-logging carbon stocks. The project goal was to determine the aboveground carbon (biomass and necromass) for a typical old-growth Eucalyptus delegatensis-dominated mixed-forest in Tasmania. Allometrics were developed for aboveground biomass of Eucalyptus delegatensis and generic rainforest understorey species. A total of 207 eucalypts with DBH 0.21–4.5 m, and 897 rainforest understorey trees with DBH 0.01–2.52 m were measured across 7.7 ha. DBH frequency distribution of E. delegatensis showed at least two age cohorts and distinct positive skew, whereas its DBH carbon distribution showed distinct negative skew. Half of the eucalypt biomass was from trees with DBH > 2.4(0.1) m, and 16% with DBH ≥ 3.5 m (from ～1.1 trees ha^?1) – indicating the importance of allometrics for high DBH. Aboveground carbon was 622(180) Mg ha^?1, with ～20% from understorey and ～25% from necromass. The carbon in aboveground biomass was above the median value for temperate forests. The long-term aboveground-carbon emissions from clearfelling the same forest type from 1999 to 2009 is likely to be 2.9(±1.3) Tg, depending on the growth and seral stages of the forest logged.     

How to map forest structure from aircraft,one tree at a time

Forest structure is strongly related to forest ecology, and it is a key parameter to understand ecosystem processes and services. Airborne laser scanning (ALS) is becoming an important tool in environmental mapping. It is increasingly common to collect ALS data at high enough point density to recognize individual tree crowns (ITCs) allowing analyses to move beyond classical stand‐level approaches. In this study, an effective and simple method to map ITCs, and their stem diameter and aboveground biomass (AGB) is presented. ALS data were used to delineate ITCs and to extract ITCs’ height and crown diameter; then, using newly developed allometries, the ITCs’ diameter at breast height (DBH) and AGB were predicted. Gini coefficient of DBHs was also predicted and mapped aggregating ITCs predictions. Two datasets from spruce dominated temperate forests were considered: one was used to develop the allometric models, while the second was used to validate the methodology. The proposed approach provides accurate predictions of individual DBH and AGB (R² = .85 and .78, respectively) and of tree size distributions. The proposed method had a higher generalization ability compared to a standard area‐based method, in particular for the prediction of the Gini coefficient of DBHs. The delineation method used detected more than 50% of the trees with DBH >10 cm. The detection rate was particularly low for trees with DBH below 10 cm, but they represent a small amount of the total biomass. The Gini coefficient of the DBH distribution was predicted at plot level with R² = .46. The approach described in this work, easy applicable in different forested areas, is an important development of the traditional area‐based remote sensing tools and can be applied for more detailed analysis of forest ecology and dynamics.     

Zonal distribution of coarse woody debris and its contribution to net primary production in a secondary mangrove forest

Coarse woody debris (CWD) plays an important role in long-term carbon storage in forest ecosystems. However, few studies have examined CWD in mangrove forests. A secondary mangrove forest on an estuary of the Trat River showed different structures along vegetation zones ranging from the river’s edge to inland parts of the forest (the Sonneratia–Avicennia, Avicennia, Rhizophora, and Xylocarpus zones, respectively). The mass distribution of CWD stock in downed wood and standing dead trees along these vegetation zones was evaluated. Most of the CWD stock in the Sonneratia–Avicennia and Avicennia zones was found in downed wood, while it mainly accumulated in standing dead trees in the Rhizophora and Xylocarpus zones. The total mass of CWD stock that accumulated in each zone ranged from 1.56–8.39 t ha^?1, depending on the forest structure and inundation regimes. The annual woody debris flux in each zone was calculated by summing the necromass (excluding foliage) of dead trees and coarse litter from 2010 to 2013. The average woody debris flux was 5.4 t ha^?1 year^?1, and its zonal variation principally depended on the necromass production that resulted from forest succession, high tree-density, and lightning. Over all the zones, the above- and below-ground net primary production (ANPP and BNPP, respectively) was estimated at 18.0 and 3.6 t ha^?1 year^?1, respectively. The magnitude of BNPP and its contribution to the NPP was markedly increased when fine root production was taken into consideration. The contribution of the woody debris flux without root necromass to the ANPP ranged from 12 to 28%.     

Composition,biomass and structure of mangroves within the Zambezi River Delta

We used a stratified random sampling design to inventory the mangrove vegetation within the Zambezi River Delta, Mozambique, to provide a basis for estimating biomass pools. We used canopy height, derived from remote sensing data, to stratify the inventory area, and then applied a spatial decision support system to objectively allocate sample plots among five strata. Height and diameter were measured on overstory trees, saplings and standing dead trees in nested plots, and biomass was calculated using allometric equations. Each of the eight mangrove species occurring in Mozambique exist within the Delta. They are distributed in heterogeneous mixtures within each of the five canopy height classes, not reflecting obvious zonation. Overstory trees averaged approximately 2000 trees ha^?1, and average basal area ranged from 14 to 41 m² ha^?1 among height classes. The composition of the saplings tended to mirror the overstory, and the diameter frequency distributions suggest all-aged stands. Above-ground biomass ranged from 111 to 483 Mg ha^?1 with 95 % confidence interval generally within 15 % of the height class mean. Despite over 3000 trees ha^?1 in the small-tree component, 92 % of the vegetation biomass is in the overstory live trees. The objective inventory design proved effective in estimating forest biomass within the 30,267 ha mangrove forest.     

Effects of soil chemistry on tropical forest biomass and productivity at different elevations in the equatorial Andes

The dependence of aboveground biomass and productivity of tropical forests on soil fertility is not fully understood, since previous studies yielded contrasting results. Here, we quantify aboveground biomass (AGB) and stem wood production, and examine the impact of soil chemistry on these parameters in mature tropical forest stands of the equatorial Andes in Ecuador. In 80 plots of 0.04 ha at four elevation levels (500, 1,000, 1,500 and 2,000 m a.s.l., total sample area = 3.2 ha), we measured ten important soil chemical parameters, inventoried all trees ≥10 cm dbh and monitored stem diameter growth with dendrometer tapes in 32 plots. Top canopy height and stem density significantly decreased from 500 to 2,000 m, while tree basal area increased and AGB remained invariant (344 ± 17 Mg DM ha^?1, mean ± SE) with elevation. Wood specific gravity (WSG) showed a significant, but small, decrease. Stem wood production decreased from 4.5 to 3.2 Mg DM ha^?1 year^?1 along the transect, indicating a higher biomass turnover at lower elevations. The only soil variable that covaried with AGB was exchangeable K in the topsoil. WSG increased with decreases in N mineralisation rate, soil pH and extractable Ca and P concentrations. Structural equation modelling (SEM) revealed that nitrogen availability acts on stem wood production only indirectly through a negative relation between N mineralisation rate and WSG, and a positive effect of a lowered WSG on stem growth. The SEM analysis showed neither direct nor indirect effects of resin-extractable P on wood production, but a negative P influence on AGB. We conclude that nitrogen availability significantly influences productivity in these Andean forests, but both N and P are affecting wood production mainly indirectly through alterations in WSG and stem density; the growth-promoting effect of N is apparently larger than that of P.     

Non‐destructive dry matter estimation of Alhagi sparsifolia vegetation in a desert oasis of Northwest China

Question: Can above‐ground biomass of naturally growing Alhagi sparsifolia shrubs be estimated non‐destructively? Location: Qira oasis (37° 01′N, 80° 48′E, 1365 ma.s.l.) at the southern fringe of the Taklamakan desert, Xinjiang, NW China. Methods: Two methods were compared to estimate above‐ground biomass (AGB) of Alhagi. At first shrub AGB was estimated by manual ground measurements (called ‘allometric approach’) of length, width and height of 50 individuals. Subsequently regression equations were established between calculated shrub canopy volume and shrub AGB (r²= 0.96). These equations were used to calculate AGB from manual ground measurements in 20 sample plots within the Alhagi field. Secondly, kite‐based colour aerial photography coupled with the use of a Geographic Information System (called ‘GIS approach’) was tested. First and second order polynomial regressions between AGB data of the 50 individual shrubs and their respective canopy area allowed to automatically calculate the AGB of all remaining shrubs covered by the photograph (r²= 0.92 to 0.96). The use of non‐linear AGB regression equations required an automatised separation of shrubs growing solitary or in clumps. Separation criteria were the size and shape of shrub canopies. Results: The allometric approach was more reliable but also more time‐consuming than the GIS‐based approach. The latter led to an overestimation of Alhagi dry matter in densely vegetated areas. However, this systematic error decreased with increasing size of the surveyed area. Future research in this field should focus on improvements of AGB estimates in areas of high shrub density.     

Long-term changes in above ground biomass after disturbance in a neotropical dry forest,Hellshire Hills,Jamaica

We used data from experimental plots (control, partially cut and clear-cut) established in 1998, in a tropical dry forest (TDF) in Jamaica, to assess changes in above ground biomass (AGB) 10 years after disturbance. The treatments reduced AGB significantly in 1999 (partially cut: 37.6 %, clear-cut: 94.4 %) and after 10 years, AGB did not recover overall, nor did it recover in the clear-cut plots. Partially cut plots, however, recovered the lost AGB in 10 years via growth of uncut trees, which contributed significantly to biomass recovery, with only minor contributions from recruited trees and coppice shoots. For clear-cut plots, coppice shoots contributed significantly to the recovered AGB when compared with recruited biomass. Together, they recovered 26 % of AGB lost, despite recovering 78 % of the density and height of the control plots. The probability of survivorship decreased for trees with higher pre-treatment AGB values, but was higher for trees with multiple stems in 1998, regardless of treatment. The magnitude of biomass reduction varied among the species assessed and this had a differential effect on their ability to recover AGB. We estimate that it will take approximately 45.4 years for the clear-cut plots to recover pre-treatment AGB; this is significantly longer than AGB recovery time for some successional rainforests on abandoned pastures/farmland. Consequently, this TDF may not be as resilient as tropical rainforests.     

Tradeoffs in basal area growth and reproduction shift over the lifetime of a long-lived tropical species

Understanding of the extent to which reproductive costs drive growth largely derives from reproductively mature temperate trees in masting and non-masting years. We modeled basal area increment (BAI) and explored current growth–reproduction tradeoffs and changes in such allocation over the life span of a long-lived, non-masting tropical tree. We integrated rainfall and soil variables with data from 190 Bertholletia excelsa trees of different diameter at breast height (DBH) sizes, crown characteristics, and liana loads, quantifying BAI and reproductive output over 4 and 6 years, respectively. While rainfall explains BAI in all models, regardless of DBH class or ontogenic stage, light (based on canopy position and crown form) is most critical in the juvenile (5 cm ≤ DBH < 50 cm) phase. Suppressed trees are only present as juveniles and grow ten times slower (1.45 ± 2.73 m² year^?1) than trees in dominant and co-dominant positions (13.25 ± 0.82 and 12.90 ± 1.35 m² year^?1, respectively). Additionally, few juvenile trees are reproductive, and those that are, demonstrate reduced growth, as do reproductive trees in the next 50 to 100 cm DBH class, suggesting growth–reproduction tradeoffs. Upon reaching the canopy, however, and attaining a sizeable girth, this pattern gradually shifts to one where BAI and reproduction are influenced independently by variables such as liana load, crown size and soil properties. At this stage, BAI is largely unaffected by fruit production levels. Thus, while growth–reproduction tradeoffs clearly exist during early life stages, effects of reproductive allocation diminish as B. excelsa increases in size and maturity.     

Above-ground biomass references for urban trees from terrestrial laser scanning data

Background and AimsWithin extending urban areas, trees serve a multitude of functions (e.g. carbon storage, suppression of air pollution, mitigation of the ‘heat island’ effect, oxygen, shade and recreation). Many of these services are positively correlated with tree size and structure. The quantification of above-ground biomass (AGB) is of especial importance to assess its carbon storage potential. However, quantification of AGB is difficult and the allometries applied are often based on forest trees, which are subject to very different growing conditions, competition and form. In this article we highlight the potential of terrestrial laser scanning (TLS) techniques to extract highly detailed information on urban tree structure and AGB.MethodsFifty-five urban trees distributed over seven cities in Switzerland were measured using TLS and traditional forest inventory techniques before they were felled and weighed. Tree structure, volume and AGB from the TLS point clouds were extracted using quantitative structure modelling. TLS-derived AGB estimates were compared with AGB estimates based on forest tree allometries dependent on diameter at breast height only. The correlations of various tree metrics as AGB predictors were assessed.Key ResultsEstimates of AGB derived by TLS showed good performance when compared with destructively harvested references, with an R² of 0.954 (RMSE = 556 kg) compared with 0.837 (RMSE = 1159 kg) for allometrically derived AGB estimates. A correlation analysis showed that different TLS-derived wood volume estimates as well as trunk diameters and tree crown metrics show high correlation in describing total wood AGB, outperforming tree height.ConclusionsWood volume estimates based on TLS show high potential to estimate tree AGB independent of tree species, size and form. This allows us to retrieve highly accurate non-destructive AGB estimates that could be used to establish new allometric equations without the need for extensive destructive harvesting.