Structural changes to forests during regeneration affect water flux partitioning, water ages and hydrological connectivity: Insights from tracer-aided ecohydrological modelling

Increasing rates of biodiversity loss are adding momentum to efforts seeking to restore or rewild degraded landscapes. Here, we investigated the effects of natural forest regeneration on water flux partitioning, water ages and hydrological connectivity, using the tracer-aided ecohydrological model EcH2O-iso. The model was calibrated using ∼ 3.5 years of diverse ecohydrological and isotope data available for a catchment in the Scottish Highlands, an area where impetus for native pinewood regeneration is growing. We then simulated two land cover change scenarios that incorporated forests at early (dense thicket) and late (old open forest) stages of regeneration, respectively. Changes to forest structure (proportional vegetation cover, vegetation heights and leaf area index of pine trees) were modelled for each stage. The scenarios were then compared to a present-day baseline simulation. Establishment of thicket forest had substantial ecohydrological consequences for the catchment. Specifically, increased losses to transpiration and, in particular, interception evaporation drove reductions in below-canopy fluxes (soil evaporation, groundwater (GW) recharge and streamflow) and generally slower rates of water turnover. The greatest reductions in streamflow and connectivity were simulated for summer baseflows and small to moderate events during summer and the autumn/winter rewetting period. This resulted from the effect of local changes to flux partitioning in regenerating areas on the hillslopes extending to the wider catchment by reducing downslope GW subsidies that help sustain summer baseflows and saturation in the valley bottom. Meanwhile, higher flows were relatively less affected, especially in winter. Despite the generally drier state of the catchment, simulated water ages suggested that the increased transpiration demands of the thicket forest could be satisfied by moisture carried over from previous seasons. The more open nature of the old forest generally resulted in water fluxes, water ages and connectivity returning towards baseline conditions. Our work implies that the ecohydrological consequences of natural forest regeneration depend on the structural characteristics of the forest at different stages of development. Consequently, future land cover change investigations need to move beyond consideration of simple forest vs. non-forest scenarios to inform sustainable landscape restoration efforts.

Evaluating Plantation Forest vs. Natural Forest Regeneration for Biodiversity Enhancement in Hong Kong

Global trends predict a continuous increase in the proportion of forest occupied by plantations up to the end of the 21st century, while a dramatic loss of biodiversity is foreseen as a result of anthropogenic exploitation and climate change. This study compares the role and performance of plantation policies in Hong Kong, with natural regeneration of secondary forest, using detailed spatio-temporal data extracted from a previous study. The study extends over a 70-year period from 1945 to 2014 using aerial photographs and satellite images of five time periods to document spatio-temporal trends in plantation forestry and natural forest succession. Field data on species richness and woody biomass at different stages of forest succession are compared with available data from plantations in the same study area. Results indicate that plantation forests support relatively few native species in the understory, with much lower species richness than naturally regenerated forest, even after 6 to 7 decades. Time-sequential maps of habitat change show that natural forest succession from barren grassy hillsides, progressed at an annual rate of 7.8%, from only 0.2% of the landscape post WWII, to over 37% today. Plantation forestry on the other hand has been less successful, and has even acted as a barrier to natural forest regeneration, as mono-cultural plantations from the late 1960s to 1980s are still plantations today, whereas other similar areas have succeeded naturally to forest. The theory of plantations acting as a nurse crop for a woody native understory is not supported, as Pinus massoniana plantations, destroyed by two deadly nematodes during the 1970s, apparently had no woody understory, as they were seen to have reverted to grassland in 1989 and are still mainly grassland today.

Structural changes to forests during regeneration affect water flux partitioning, water ages and hydrological connectivity: Insights from tracer-aided ecohydrological modelling

Increasing rates of biodiversity loss are adding momentum to efforts seeking to restore or rewild degraded landscapes. Here, we investigated the effects of natural forest regeneration on water flux partitioning, water ages and hydrological connectivity, using the tracer-aided ecohydrological model EcH2O-iso. The model was calibrated using ~3.5 years of diverse ecohydrological and isotope datasets available for a catchment in the Scottish Highlands, an area where the impetus for regeneration of native pinewoods is growing. We then simulated two land cover change scenarios that incorporated forests at early (thicket) and late (old-open forest) stages of regeneration, respectively, and compared these to a present-day baseline simulation. Changes to forest structure (proportional vegetation cover, vegetation heights and leaf area index of pine trees) were modelled for each stage. Establishment of thicket forest had the greatest effect on water partitioning/ages and connectivity, with increased losses to interception evaporation driving reductions in below-canopy fluxes (soil evaporation, groundwater recharge and streamflow) and generally slower rates of water turnover. Effects on streamflow were most evident for low and moderate summer flows rather than winter high flows. Whilst full forest regeneration was limited to hillslopes, resultant changes to the spatial dynamics of flux partitioning could also cause drying out of the valley bottom. The more open nature of the older forest generally resulted in water fluxes, ages and connectivity characteristics returning towards baseline conditions. Our work implies that the ecohydrological consequences of natural forest regeneration on degraded land depend on the structural characteristics of the forest at different stages of development. Consequently, future land cover change investigations need to move beyond consideration of simple forest vs. non-forest scenarios to inform management that effectively balances landscape restoration with demand for ecosystem services. Tracer-aided ecohydrological models were also shown to be useful tools for land cover change simulations and further potential of such models was highlighted.

Variation Between Voivodships in Terms of Forest Area and Silviculture Activities in Polish Forests in 2015-2019

The objective of the study reported here was to compare voivodships in terms of forest area, forest regeneration area, afforested area, thinned forest area and natural forest regeneration area Main Statistical Office data for Polish voivodships was analysed. It included forest area, natural forest regeneration and silviculture activities (forest regeneration, afforestations and thinning) in all forests, state-owned forests and privately-owned forests. Voivodships were compared using the arithmetic mean, the indicator of structure, the average rate of change, principal component analysis and cluster analysis. Principal Component Analysis, revealed that state-owned forest area, forest regeneration in state forests, total forest regeneration, and thinning in state-owned forests had the greatest share in the multivariate variation among voivodships analysed in terms of forestry. Cluster analysis yielded two groups of voivodships. The voivodships in the first group had a higher average total forest area, area of state-owned forests, total area of forest regeneration and forest regeneration in state-owned forests, area of natural forest regeneration and thinning in state-owned forests. On average, forests of voivodships which formed group 2 included less privately-owned forests in which fewer forest regeneration and afforestation activities had been conducted. Opolskie and Śląskie Voivodships as well as Łódzkie and Świętokrzyskie Voivodships were the most similar in terms of all the analysed characteristics.

Natural forest regeneration on the cuttings of Karelia due to fertility and moisture forest soil

Цель исследования – выявить влияние эффективного плодородия и увлажнения лесных почв на успешность последующего естественного лесовозобновления на вырубках Карелии. Эффективное плодородие лесных почв, по профессору О.Г. Чертову, – это отношение мощности гумусового горизонта к мощности лесной подстилки (гумусо-подстилочный коэффициент, ГПК). На вырубках давностью 5–15 лет величина ГПК закономерно возрастает по исходным типам леса от бедных (ГПК = 0,2) к сравнительно богатым местообитаниям (ГПК = 1,3–1,5). При этом изменяются густота и состав подроста. Наибольшая общая густота подроста (18 тыс. экз./га) характерна для почв среднего плодородия, с некоторым переувлажнением – в исходном типе леса ельник черничник влажный (ГПК = 0,3). Подрост ели последующего возобновления присутствует на вырубках в незначительном количестве или полностью отсутствует. Исключение составляет тип леса ельник черничник влажный, где густота подроста ели – 2,5–3 тыс. экз./га – достаточна для естественного восстановления ели на вырубках. В этом типе леса наблюдается также наибольшая густота подроста березы – в среднем 12,6 тыс. экз./га. Подрост сосны последующего возобновления имеет наибольшую густоту (2 тыс. экз./га) в самых бедных и сухих лесорастительных условиях – в исходном типе леса сосняк беломошник (ГПК = 0,2), где у сосны мало конкурентов. Подрост осины имеет слабую связь с почвенным увлажнением; его наибольшее количество (6,5–9 тыс. экз./га) имеется в относительно богатых почвенных условиях в исходном типе леса кисличник (ГПК = 1,3–1,5). По исходным типам леса и составу древостоя, определяющим эффективное плодородие почв, можно уверенно прогнозировать успешность последующего естественного лесовосстановления на вырубках. Однако в подавляющем большинстве типов леса Карелии количество хвойного подроста последующего возобновления является недостаточным для формирования хвойных древостоев без дополнительных лесохозяйственных мероприятий. The aim of the study is to identify the impact of effective fertility and forest soil moisture on the success of subsequent natural reforestation on the logging of Karelia. Effective fertility of forest soils by Professor O.G. Chertov is the ratio of the thickness of the humus horizon to the thickness of forest litter (humus-litter ratio, HLR). On the cuttings of the long ago 5–15 years old, the value of the HLR naturally increases by the original types of forest from poor (HLR = 0.2) to relatively rich habitats (HLR = 1.3–1.5). At the same time, the density and composition of the undergrowth change. The greatest total density of growth (18 thousand ex./ha) is typical for the soils of average fertility, with some overhydration – in the original type of forest Spruce blueberry wet (HLR = 0.3). Natural reforestation of Spruce of subsequent resumption growth is present on the cuttings in small amounts or completely absent. The exception is the type of forest Spruce blueberry wet, where the density of spruce undergrowth – of the ate – 2.5–3 thousand. ex./ha – enough for the natural restoration of spruce on felling. In this type of forest also there is the greatest density of birch growth – an average of 12.6 thousand. ex./ha. The natural reforestation of the pine of subsequent renewal has the greatest density (2 thousand ex./ha) in the poorest and driest forest conditions – in the original type of forest pine white-pine (HLR = 0.2), where the pine has few competitors. The natural reforestation of aspen has a weak association with soil hydration; its largest number (6.5–9 thousand ex./ha) is available in relatively rich soil conditions in the original type of forest wood sorrel (HLR = 1,3–1.5). By the original types of forest and the composition of the tree, which determines the effective fertility of the soils, it is possible to confidently predict the success of subsequent natural reforestation on the felling. However, in the vast majority of Karelia forest types, the amount of coniferous growth is not sufficient to form coniferous woodlands without additional forestry activities.

OVERVIEW OF DESIGNS OF TREE-PLANTING MACHINE FOR OPEN AREAS AND CLEARED FELLING

Reforestation is the main, priority task of the modern forest complex. Natural forest regeneration has long been considered a priority. Natural regeneration, as a way of reforestation, has a number of significant drawbacks. Firstly, the natural regeneration of forests in burned areas and deforestation does not occur immediately after deforestation, but over a fairly long time ̶ reforestation period, during which various unfavorable processes ̶ soil erosion, sodding develop on an unforested area. Secondly, natural renewal quite often leads to a change of species, i.e. desired valuable breeds do not grow. As a result, the territory is overgrown with minor soft-leaved species that have low economic value. Mechanized landing, i.e. artificial reforestation, also has a number of disadvantages. Therefore, planting operations carried out under various conditions are the most labor-intensive and responsible operations. The technological process of planting seedlings and seedlings of various tree species with both open and closed root systems is presented. The analysis of existing designs of forest planting machines for open areas, fires and clearings is carried out. Deficiencies were identified that affect the quality of the planting process and reduce the survival rate of planted seedlings and seedlings.