Understanding some of the causes of widespread forest decline: what we know, and what (I think) we need to know

Transcription

1 Impactos, Vulnerabilidad y Adaptación de los Bosques y la Biodiversidad de España frente al cambio climático CENEAM, Valsaín, Segovia (28-29 mayo 213) Understanding some of the causes of widespread forest decline: what we know, and what (I think) we need to know Jesús Julio Camarero ARAID-Instituto Pirenaico de Ecología (CSIC) Pinyon Pine Decline, massive forest die-off in US SW

2 1. No forest type or climate zone is invulnerable to anthropogenic climate change, even in environments not normally considered waterlimited. 2. Our data are consistent with the possibility that climate change is contributing to an increase in reported mortality. SE Spain Colorado NW Africa, cedar Argentina New Mexico Climate-induced forest die-off Sources: van Mantgem et al. (29), Allen et al. (21), Anderegg et al. (212)

3 Manion (1991) conceptual model. Decline is caused by interacting abiotic and biotic factors (decline disease spiral) classified in three groups: PREDISPOSING factors: long-term drivers (climate, site, soil, age, genetic pool, historical use). Reduce tree vigor. INCITING factors: short-term stressors (reduce C storage, enhance branch mortality and casue defoliation) such as droughts, frosts, insects, mechanical damages. CONTRIBUTING factors: opportunistic (secondary) organisms which contribute to kill the already weakened tree (e.g., root fungi, scolitids, etc.). Manion (1991, 22)

4 STUDY CASE 1 A France Spain Km B ANS ECH ARA CAN CAS BIE YES TOR PIN SJP BEN SEI Km Camarero et al. (211), Linares and Camarero (212)

5 STUDY CASE 1: defoliation (W-E spatial pattern) 43. WINTER GA SO SZ IA PA 42.9 PZ PE PC AB 42.8 LO PM2 LI DZ 42.7 VI YE PM1 AS SN BA FA CA 42.6 OR AZ SA PN 42.5 PO CO 42.4 JP OO GU SPRING SUMMER FALL Precipitation (%) Winter Spring Summer Fall Camarero et al. (211), Linares and Camarero (211, 212)

6 STUDY CASE 1: drought (mid 198s) Mean annual temperature (ºC) Annual precipitation (mm) Annual water deficit (mm) Year Camarero et al. (211), Linares and Camarero (211, 212)

7 STUDY CASE 1: Growth patterns. Tree-ring width (mm) Basal-area increment (cm 2 ) a b All sites Declining sites Non-declining sites Year No. radii 6 3 Camarero et al. (211), Linares and Camarero (211, 212)

8 STUDY CASE 1: HISTORY as a predisposing factor: more dying trees in formerly more intensively logged stands. 6 Lopetón (Ansó) Tree-ring width (mm 1-2 ) LO1 (dead tree + 197s releases) Years Camarero et al. (211)

9 STUDY CASE 2: Scots pine (Pinus sylvestris) decline in the Iberian System (Gúdar Range, Teruel, E Spain). Declining Healthy

10 STUDY CASE 2: : Dieback (more defoliation & mortality) was more severe in S than in N-oriented slopes (and also within tree crowns in flat areas). Defoliation & sapwood area were negatively related In S-oriented slopes Growth driven by competition in N-oriented slopes Declining Healthy Ca. 5% trees died in S-oriented slopes.

11 STUDY CASE 2: Since 22 ongoing dieback is observed in the study area. Healthy and Affected trees are located sideby-side and they are distributed randomly. Declining We are close to the rear edge or southernmost limit of the species distribution area. Healthy Gúdar Range

12 STUDY CASE 2: Triggering factor: anomalous autumn-winter in October 1 5 Temperature (ºC) 1 5 October December December Day

13 STUDY CASE 2: Triggering factor: anomalous autumn-winter in 21. Absolute minimum December T (ºC) Time (years) Estimated 1-year return level (95% CIs) Mean -1 SD -2.5 SD Frost or winter drought

14 STUDY CASE 2: Pre-dieback differences: BAI. 15 Basal-area increment (cm 2 yr -1 ) 1 5 ND D During the mature phase and until the decline episode in 22, declining trees (D) grew faster than healthy ones (ND) (same pattern when comparing S- vs-n-oriented slopes).

15 STUDY CASE 2: Some conclusions. 1) Healthy and declining trees show a differential previous history in growth and water relations (higher sensitivity in declining trees). 2) After the anomalous 21 autumn-winter, a critical threshold of plasticity for WUE was reached.