Plant diversity on skid trails in oak high forests: A matter of disturbance, micro-environmental conditions or forest age?

Abstract

29 Increasingly mechanized timber harvesting and the repeated use of skid trail 30 networks may affect ground vegetation differently at subsequent stages in the forest 31 rotation. At a fine scale, no studies have yet compared the influence of 32 micro-environmental factors and the effects of skid trail disturbance on ground flora 33 diversity. We investigated understory diversity patterns on skid trails in 30-, 50-and 34 63-year-old oak forests in the northern half of France. Subplots were placed on skid 35 trail center, wheel track, skid trail edge plus an off-trail control. At each subplot, we 36 measured soil moisture, soil compaction (penetration resistance and bulk density) and 37 photosynthetic active radiation and recorded the abundance of all vascular plants. The 38 richness and abundance of ground flora were calculated based on the classification of 39 their life form, seed bank persistence, light preference and moisture requirements. For 40 each ecological group, we found out its best diversity indicator from subplot location, 41 micro-environmental factors (soil moisture and compaction, light) and stand attributes 42 (stand type, basal area), then assessed the magnitude and negligibility of the effect of 43 the best indicator. 1) Higher soil compaction compared to controls was detected on 44 the tracks of skid trails in the 50-and 63-year-old stands. Neither soil moisture nor 45 light varied with subplot location whatever the stand type. 2) The best diversity 46 indicator that showed non-negligible effects included subplot location, and soil 47 moisture or soil compaction. Compared to controls, skid trails in the 50-and 48 63-year-old stands were richer in tree and short-term seed bank species, while skid 49 trails in the 30-year-old plots had no effect on ground flora. The abundance of tree 50 and shade-tolerant species was also higher on skid trails. Soil moisture was positively 51 correlated with the richness of low-and high-humidity species, shade-tolerant species 52 and transient seed bank species as well as with the abundance of short-term seed bank 53 species. Bulk density positively affected heliophilous species richness, while 54 penetration resistance was positively related to shrub abundance. Skid trails and soil 55 compaction in our research area had either no impact or a positive impact on ground 56 flora diversity. Longer-term studies of skid trail effects are needed to validate these 57 main findings.58 59

Soil Compaction Effects on Root‐Zone Hydrology and Vegetation in Boreal Forest Clearcuts

“…The following data were recorded for each of the 117 vegetation plots: a track depth (microsite WT), the area of ponded water (%), the area with bare soil (%), heights of planted pine seedlings (if present) and self‐seeded seedlings of pine or other tree species. Finally, the occurrence of species and their cover (at estimated full seasonal development) were recorded according to the Braun‐Blanquet abundance‐dominance classification (as it is described by Wei et al, 2015): i , one individual, the cover <5%; +, very few individuals, the total cover <5%; 1, few to many individuals, the total cover <5%; 2, many individuals, the total cover 5 to 25%; 3, the total cover 25 to 50%; 4, the total cover 50 to 75%; and 5, the total cover >75%. The seven coefficients were later transformed into the following percentile cover values: i , 0.1%; +, 0.5%; 1, 5%; 2, 17.5%; 3, 37.5%; 4, 62.5%; and 5, 87.5% (Wei et al, 2015).…”

“…Finally, the occurrence of species and their cover (at estimated full seasonal development) were recorded according to the Braun‐Blanquet abundance‐dominance classification (as it is described by Wei et al, 2015): i , one individual, the cover <5%; +, very few individuals, the total cover <5%; 1, few to many individuals, the total cover <5%; 2, many individuals, the total cover 5 to 25%; 3, the total cover 25 to 50%; 4, the total cover 50 to 75%; and 5, the total cover >75%. The seven coefficients were later transformed into the following percentile cover values: i , 0.1%; +, 0.5%; 1, 5%; 2, 17.5%; 3, 37.5%; 4, 62.5%; and 5, 87.5% (Wei et al, 2015). The species were divided into the following groups: self‐seeded tree seedlings, Ericaceae , graminoides (species with grass‐like morphology), mosses, and other species (Appendix ).…”

“…Soil moisture availability is also important for predicting species composition of the ground vegetation (Härdtle et al, 2003). Wei et al (2015) found that soil moisture in skid trails was positively correlated with the number of species that prefer moist or wet conditions.…”

“…Soil moisture availability is also important for predicting species composition of the ground vegetation (Härdtle et al, 2003). Wei et al (2015) found that soil moisture in skid trails was positively correlated with the number of species that prefer moist or wet conditions. Ground vegetation responds rapidly and at fine scales to management practices and disturbances, and thus, it is suitable for detecting changed soil conditions caused by off-road traffic (Duguid and Ashton, 2013).…”

Light Intensity and Soil Compaction as Influenced by Ecotourism Activities in Pahang National Park, Malaysia

“…According to other previous studies [33,34], tree root growth for many plants becomes restricted when soil penetration resistance exceeds 2.00 MPa and stops at resistances greater 3.00 MPa. Many previous studies were agreed that a range of 2.00-3.00 MPa of soil compaction is affecting the pattern of tree growth, but study in oak forests in the northern half of France by Wei et al [35] found the higher soil compaction detected on skid trails, which does not necessarily mean that it will have significant effects on ground flora. This is because flora could survive with penetration resistance to the ground up to 2.5 MPa.…”