Variability in soil CO2 fluxes across a range of forest types and edaphic conditions

<p>Forests play a key role in the global carbon (C) balance. On the one hand, a large amount of C is sequestered in soils, and on the other hand, the forest soils are also a significant source of carbon dioxide (CO<sub>2</sub>). Soil respiration includes anaerobic and aerobic microbial respiration, and root respiration which may contribute even more that half of the total soil respiration. Assessment of the contribution of forest soils to CO<sub>2</sub> emissions, in addition to C sequestration, is worth special attention in the context of increasing climate change. To address this field experiments were carried out to assess the CO<sub>2</sub> fluxes of 10 different forest soil types with different tree species (deciduous, coniferous, and mixed) in Poland (using static chamber method). The highest CO<sub>2</sub> emissions were observed for a silty soil under the youngest deciduous forest (12 y.) with a  daily average of 1.66 ± 0.7 g CO<sub>2</sub> m<sup>-2</sup> d<sup>-1</sup>. The lowest daily mean CO<sub>2</sub> flux was associated with a sandy soil in a mature stand of a predominantly coniferous forest (0.87 ± 0.3 g CO<sub>2</sub> m<sup>-2</sup> d<sup>-1</sup>). Annual averages were in the range 3.21 t C ha<sup>-1</sup> to 6.06 t C ha<sup>-1</sup> for a mature and young forest, respectively. The main factor causing differences in CO<sub>2</sub> emissions could have been the contribution of both trees and soil properties to hydrological conditions. The young forest was covered with trees with a lower root system forest and the young trees could have a lower demand for water resulting in a higher soil moisture content than in a mature forest soil. Different CO<sub>2</sub> fluxes could be also a result of a higher water storage capacity in silty soil in the young forest than that of a sandy soil under mature stand. In addition to water supply, the activity of soil microorganisms is also regulated by C availability which was about 30% lower in sandy soil than in silty soil. The two-yearly measurements showed seasonal variations in CO<sub>2</sub> fluxes depending on the soil type, age and tree species. Regardless of the characteristics of the forest being studied, the highest CO<sub>2</sub> emissions occurred in the summer or spring and the lowest CO<sub>2</sub> emissions were found  in winter as a result of a strong influence of temperature on the biological processes under investigation. The observed seasonality in CO<sub>2</sub> emission may be attributed to changes in soil moisture during the measurement periods since soil water content regulates microbial activity and gaseous diffusion. Statistical analyses, however, imply that temperature could have  a stronger control over CO<sub>2</sub> emissions from the soils studied than soil moisture.</p><p>Research was conducted under the project financed by Polish National Centre for Research and Development within of ERA-NET CO-FUND ERA-GAS Programme (ERA-GAS/I/GHG-MANAGE/01/2018) “GHG-Manage”.</p>

Ground vegetation composition and diversity in drained Norway spruce (Picea abies (L.) Karst.) stands 50 years after whole-tree harvesting management: case study in Latvia

The long-term (50 years) effect of whole-tree harvesting (stump harvesting) on ground vegetation in experimental drained Norway spruce (Picea abies (L.) Karst.) stands was studied. We used a chronosequence approach to assess the long-term impact of whole-tree harvesting (WTH) on stands’ ground vegetation. WTH stands were compared with four control stands with different age and with the same forest type: young stand (15 years), middle-aged stand (45 years), mature stand (110 years) and over-mature stand (140 years). Species richness was similar between the WTH stand and middle-aged stand (61 and 60 species, respectively). Shannon-Wiener diversity indices in the WTH and middle-aged stand (3.40 and 3.19, respectively) indicated that the stands were similar to each other. A community similarity analysis showed that the composition of vegetation was similar between the WTH and middle-aged stand, although some species like Lycopodium clavatum and Diphasiastrum complanatum occurred only in the WTH stand. The study showed that a period of 50 years is sufficient for ground vegetation of a typical drained spruce forest to recover after WTH management.

Disturbance macroecology: integrating disturbance ecology and macroecology with different-age post-fire stands of a closed-cone pine forest

Macroecological studies have generally restricted their scope to relatively steady-state systems, and as a result, how biodiversity and abundance metrics are expected to scale in disturbance-dependent ecosystems is unknown. We examine macroecological patterns in a fire-dependent forest of Bishop pine (Pinus muricata). We target two different-aged stands in a stand-replacing fire regime, one a characteristically mature stand with a diverse understory, and one more recently disturbed by a stand-replacing fire (17 years prior to measurement). We compare the stands using macroecological metrics of species richness, abundance and spatial distributions that are predicted by the Maximum Entropy Theory of Ecology (METE), an information-entropy based theory that has proven highly successful in predicting macroecological metrics across a wide variety of systems and taxa. Ecological patterns in the mature stand more closely match METE predictions than do data from the recently disturbed stand. This suggests METE’s predictions are more robust in late-successional, slowly changing, or steady-state systems than those in rapid flux with respect to species composition, abundances, and organisms’ sizes. Our findings highlight the need for a macroecological theory that incorporates natural disturbance and other ecological perturbations into its predictive capabilities, because most natural systems are not in a steady state.

SUCCESSION OF GROUND COVER VEGETATION IN HYLOCOMIOSA FOREST SITE TYPE AFTER THE CLEARCUT

Nowadays forestry sector uses forest site type descriptions developed from beginning of 20th century till 1980’s and descriptions are obtained for pre-mature and mature stand age. There is less information about ground cover vegetation for full rotation cycle. In this research has been gathered information about ground cover vegetation succession in first 5 years after clear cut in mature Scots pine stand. The chronosequence method was used. The Brown-Blanquet and the point-square methods for accounting of ground cover plants were used. The ecological values of Ellenberg for describing the environmental status and the coefficient of Tschekanovsky for estimation of the difference between plant communities in forest young growths of different age were used. The biological diversity of species in this research compared to mature stand also is increasing. Ellenberg’s ecological indicator values as light and nitrogen are also increasing: nitrogen value has increased the most - by 2.62 units. There are registered changes in vascular plants, mosses, lichens and trees projective covering’s proportion. The most significant changes in individual species occurrence are between the second and third year's (Tschekanovsky coefficient = 0.19). Five years after clear cut the Tschekanovsky coefficient between the mature stand and five years old clearing is 0.18. In the 4th and 5th year after the clear cut there increase the projective cover of Monocotyledonae plants (families Graminaea and Cyperaceae) forming higher vertical structure and overtaking the dominance from another groups. The results obtained in this research promote further research in different stand age.

Stand density management and blue carbon stock of monospecific mangrove plantation in Bohol, Philippines

Blue carbon pertains to carbon stock that is stored by marine ecosystems including mangrove forest. Density and blue carbon stock assessment was conducted covering matureRhizophora stylosaGriff. plantations in Bohol, Philippines. Three stand types were assessed: thinned mature stand (0.34 tree m−2at 55 years old; 35 ha); non-thinned mature stand (1.2 tree m−2at 55 years old; 20 ha) and young stand (2.6 tree m−2at 20 years old; 150 ha). These plantations were initially established with a plant spacing of 0.5 m × 0.5 m. Non-destructive plot sampling technique was used to account biomass and carbon stocks of trees and sediments. Five (5) sample plots measuring 200 m2were allocated for each stand type. Results showed that the total carbon stock of plantations amassed to 64.5 ktC or 236.6 ktCO2e. More than half (at least 54%) of this stock is imbedded in sediment. Individual accounts showed that carbon stock was largest in non-thinned stand with 435.2 tC ha−1, followed by thinned stand (408.5 tC ha−1) and young stand (276.8 tC ha−1). There was no significant difference between thinned and non-thinned mature stands carbon stocks. Such finding suggested the potential of having thinning intervention. Following the self-thinning rule of 1.1 to 1.3 tree m−2, the local community can harvest as much as 423 trees ha−1yr−1for 35 years starting at the plantation age of 20 years. Further, the additional carbon stock between the ages 20 to 55 years could reach about 580 tCO2e ha−1with an economic value of USD 2,962 ha−1. With this potential benefits, it is recommended that Banacon Island should pursue a carbon offset project for its plantations.

Soil Humus Compositions and the Influence on Soil Acidity in Larix olgensis Plantation of NE China

Variation in soil humus compositions (SHC) and the effect on soil acidity (SA) were studied in LOP of NE China. The results showed that for rhizosphere soil (RS) and non-rhizosphere soil (NRS), soil organic matter (SOM), carbon (C) in humic acid (HA) and humin increased from young stand (YS) to near mature stand (NMS) over ages, however, SOM, C in fulvic acid (FA) and humin decreased from NMS to mature stand (MS). Soil humification degree (SHD) were higher in secondary forests than in YS and NMS. As compared with young stand in the first rotation (YSFR), for RS, SOM, C in FA and humin decreased by 4.53%, 35.8% and 1.98% in young stand in the second rotation (YSSR), respectively, but for NRS, SOM, C in HA, FA and humin increased by 46.44%, 43.69%, 47.45% and 49.5%, respectively. Correlation between SHC and SA changed over ages. In RS, close correlation existed among SHC, active acidity (pH, AA), exchange and hydrolytic acidity at different development stages (DDS).

Variation in Soil Acidity in Larch Plantations in Eastern Montane Area of Northeast China and its Effect on Soil Phosphorus Forms

Variations in SA in various stands of first rotation larch plantation (FRLP) at different development stages (DDS), and in young stand (YS) of second rotation larch plantation (SRLP) in eastern montane area of northeast China and the relationship between SA and various forms of OP and IP were studied. Our results demonstrated that soil active acidity (pH value, SAA) in rhizosphere soil (RS) decreased continually with increasing stand ages from YS, half-mature stand (HMS), near mature stand (NMS) to mature stand (MS), but SAA in non-rhizosphere soil (NRS), exchange acidity (EA), exchangeable aluminium (EAL), total hydrolytic acidity (THA), and the ratio of EA to THA in RS and NRS increased apparently; when SA increased, total organic phosphorus (TOP), moderately resistant organic phosphorus (MROP), and highly resistant organic phosphorus (HROP) decreased in all stands of FRLP. For all stands except in HMS, when EA in RS increased, TOP, MROP, and HROP decreased. The correlation between labile organic phosphorus (LOP) and SAA, THA in RS reached highly significant level (HSL) at P=0.01 or significant level (SL) at P=0.05, respectively. Correlation coefficient (CC) between LOP and THA in RS diminished as stand ages increased. Positive correlation between moderately liable organic phosphorus (MLOP) and SAA in RS reached SL at P=0.05 or HSL at P=0.01 in all stands. In most stands, the close correlation existed between MROP and soil potential acidity (SPA), and between HROP and SPA, respectively.

Variation in Soil Phosphorus Forms in Larix olgensis Plantations in Eastern Montane Area of Northeast China

Variation in total phosphorus (TP), available phosphorus (AP), the forms of organic phosphorus (OP) and inorganic phosphorus (IP) in rhizosphere soil (RS) and non-rhizosphere soil (NRS) at different development stages in larch (Larix olgensis) plantations was quantitively studied through field investigation, chemical analysis and statistical test. The results indicated that: AP, O-P (occluded phosphate), TP, OP in RS exhibited a significantly or apparently decreased tendency over stand age, but IP, Ca-P (phosphate combined with calcium) and Fe-P (phosphate combined with Ferrum) in RS presented a significantly or apparently increased trend when stand age increased; Ca-P in NRS increased when stand age became larger; Fe-P in half-mature stand (HMS), AP and Fe-P in near mature stand (NMS), AP and Ca-P in mature stand (MS) in NRS was higher than in RS