Forest gaps retard carbon and nutrient release from twig litter in alpine forest ecosystems

Self Cite

Changes in the microenvironment induced by forest gaps may affect litter decomposition, yet it is unclear how the gap effects respond to altitudinal and seasonal differences. Here, a four-year litterbag decomposition experiment along an elevation gradient (3000, 3300, 3600 m) was conducted in an Abies faxoniana Rehd. subalpine forest of southwestern China, to assess the potential seasonal effects of forest gaps (large: ≈250 m2, middle: ≈125 m2, small: ≈40 m2 vs. closed canopy) on litter mass loss and carbon release at different elevations. We found that the A. faxoniana litter mass loss and carbon release reached 50~53 and 58~64% after four years of decomposition, respectively. Non-growing seasons (November to April) had a greater decline than the growing seasons (May to October). Litter in the forest gaps exhibited significantly higher mass loss than that under the closed canopy, and the decomposition constant (k) exhibited a gradually declining trend from large gaps, middle gaps, small gaps to closed canopy. Moreover, more significant differences of gap on both carbon content and release were observed at the 3600 m site than the other two elevations. Our findings indicate that (i) a rather high mass loss and carbon release during the decomposition of A. faxoniana litter was observed at high elevations of the subalpine forest subjected to low temperatures in the non-growing seasons and (ii) there were stimulative effects of forest gaps on litter mass loss and carbon release in early decomposition, especially in the non-growing seasons, driven by fewer freeze–thaw cycles when compared to the closed canopy, which diminished at the end of the experiment. The results will provide crucial ecological data for further understanding how opening gaps as a main regeneration method would induce changes in carbon cycling in subalpine forest ecosystems.

Section: Discussionsupporting

confidence: 76%

Section: Introductionmentioning

confidence: 99%

Effects of Forest Gaps on Abies faxoniana Rehd. Leaf Litter Mass Loss and Carbon Release along an Elevation Gradient in a Subalpine Forest

Chen

et al. 2022

Self Cite

“…Natural gaps in overstorey canopies result in environmental changes for the understorey beyond effected by light and nitrogen availability. In particular, the understorey microclimate above and below ground is largely controlled by species-specific characteristics and the spatial structure and temporal dynamics (phenology) of overstorey canopies [20,21,53]. Light irradiance and quality in forest gaps often follow strong diurnal patterns [40], and vegetation dynamics in natural gaps are also strongly shaped by biotic interaction between a range of co-occurring vegetation components and plant-animal interactions, including herbivory [54].…”

Section: Discussionmentioning

confidence: 99%

“…For example, previous studies evidenced that pronounced gaps impact the soil temperature and moisture on the forest floor of gap centers [20,21], significantly enhancing the nutrient release (i.e., N, P, and K) and mass loss from litter decomposition during the vegetation period [14,22]. Similarly, N availability in larger gaps in temperate ecosystems is often increased due to modified snow cover, soil freezing, and thawing events-regulating litter decomposition and facilitating nutrient release during the winter [21,23,24]. Furthermore, soil N availability in gaps may increase by a reduced uptake by a less dense plant cover [14]-further facilitated by ever-increasing dry and wet N deposition rates in some regions of the world, including northeast China [22].…”

Section: Introductionmentioning

confidence: 99%

Correlation of Leaf and Root Traits of Two Angiosperm Tree Species in Northeast China under Contrasting Light and Nitrogen Availabilities

Khan

Zarif

Yang

et al. 2021

Light and nitrogen availability are among the most important environmental factors influencing leaf and root morphological traits and forest ecosystems. Understanding the variation in leaf and root traits is pivotal to the adaptive plasticity and leaf-root-specific traits in response to low light and N availability. The effects of light and N availability on leaf and root traits and their interrelations are still not clear. We aimed to measure the response of leaf and root traits and their interrelations to light and N availability in a temperate region. Thus, a factorial experiment was conducted with two angiosperm tree species under two light (L+, L−) and two nitrogen (N−, N+) levels. Results showed that the leaf density (LD) and leaf mass per area (LMA) increased, while leaf thickness (LT) decreased under low light availability. Under N availability, the LD and LMA decreased, while LT increased in sun-exposed plots and remained stable under low light availability across two species. The root diameter, root length, specific root length (SRL), and specific root area (SRA) decreased, while the root tissue density (TD) increased under low light availability. Root diameter, root length, SRA, and SRL increased, while the TD decreased under N+ in L+ plots and remained stable under L− plots. LMA and LT were significantly positively correlated to root length and SRL while significantly negatively correlated to TD. However, LD was significantly positively correlated to TD. We observed that low light availability has significantly decreased the plant biomass and root mass fraction (RMF) and increased the leaf mass fraction (LMF), while the stem mass fraction (SMF) remained stable―indicating the shade in-tolerances in both species. Correlation analyses revealed that LMF is generally, and particularly under L− conditions, less related to leaf and root morphological traits, while RMF was frequently positively correlated to both leave and root traits under all environmental conditions. This illustrates a divergent regulation of morphological traits above and below ground under varying biomass allocation patterns.

“…Gap is an important driving force for natural regeneration of forests, an important channel for regulating the reorganization of plantation vegetation and plays an important role in vegetation succession and nutrient cycling in forest ecosystems [52]. On the one hand, the formation of gaps can affect the microenvironment below the canopy, the invasion and settlement of plants, and the regeneration of understory vegetation, thereby changing the stand structure, which may exert a strong effect on the soil stoichiometric characteristics of gaps [53]. On the other hand, compared with the canopy forest, the formation of gaps changes the water and heat dynamics and the community structure of decomposers in the forest, which can affect the nutrient utilization and turnover efficiency (such as litter decomposition) of the understory vegetation, and then profoundly affects the soil nutrients' distribution pattern [54].…”

Section: Effects Of Different Forest Gap Ages On Soil Stoichiometric ...mentioning

confidence: 99%

Effects of Different Forest Gap Ages on Soil Physical Properties and Stoichiometric Characteristics in Cryptomeria japonica plantations (L.f.) D.Don, 1839

Xiao

Wang

Yuan

et al. 2022

In this study, the evergreen plant Cryptomeria japonica (L.f.) D.Don, 1839 forest gap in the subtropical region of China were taken as the research object. The effects of different forest gap ages (<10 years, 10–20 years, >20 years) on soil physical properties and stoichiometric characteristics were analyzed in Lushan Mountain, China. With the increase of forest gap ages, the physical properties of soil surface layer in forest gap were improved, and the water holding capacity of soil was enhanced. The capillary porosity and total porosity of soil increased significantly, and the soil bulk density of 10–20 cm soil layer decreased. The increase of forest gap recovery years is beneficial to the increase of large particle size soil aggregates, and the increase of large particle size aggregates has a good effect on improving soil structure. The contents of carbon (C), nitrogen (N), and phosphorus (P) in soil showed an overall increasing trend with the increase of forest gap age and were significantly higher than those of Cryptomeria japonica pure forest (p < 0.05). The nutrient content of forest gap in 10–20 years was the highest, and the nutrient content of 0–10 cm soil layer was generally higher than that of 0–20 cm soil layer. The C:P and N:P in the soil showed an overall decreasing trend, while C:N was significantly smaller than other age gaps in 10–20 years. The results showed that soil physical properties and stoichiometric characteristics were improved with the increase of forest gap ages.